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Transcript of Forging Operations
Forging Operations
MACHINE FORGINGFORGING DIES
SPECIAL FORGING OPERATIONS
207
Published by
INTERNATIONAL TEXTBOOK COMPANYSCRANTON. PA.
io-s.(cO¥H
T6tis.Fl .
Machine Forging: Copyright, 1916, 1906, by International Textbook Company.
Forging Dies: Copyright, 1916, by International Textbook Company.
Special Forging Operations: Copyright, 1916, 1906, by International Textbook
Company.
Copyright in Great Britain
All rights reserved
Printed in U. S. A.
^'^-^^oy^^
International Textbook Press
Scranton, Pa.
93734
CONTENTSNote.—This book is made up of separate parts, or sections, as indicated by
their titles, and the page numbers of each usually begin with 1. In this list ofcontents the titles of the parts are given in the order in which they appear inthe book, and under each title is a full synopsis of the subjects treated.
MACHINE FORGING Pages
Forging Machines 1-51
Introduction 1
Rolls 2-11
Hammers 12-30
Swaging Machines 31
Presses 32-36
Upsetting Machine 37-41
Punches and Shears 42-46
Riveting Machines 47-49
Bulldozer 50-51
FORGING DIES
Forms of Forging Dies 1-34
Drop-Forging Dies 1-28
Heading and Bending Dies 29-34Heading-machine dies ; Bending dies.
Construction of Forging Dies 35-56
Materials and Equipment 35^6Die-Making Operations 47-56
SPECL\L FORGING OPERATIONSHeating Furnaces 1-1
1
Miscellaneous Operations and Data 12-53
F'orging Structural Shapes 12-16
Effect of Repeated Heating on Metal 17
Estimating Stock 17-33
iv CONTENTS
SPECIAL FORGING OPERATIONS— {Continued)
Pages
Thermit Welding 34-49
Table of Weights per Linear Foot and Areas of Square
and Round Steel Bars 50-51
Table of Weights per Linear Foot of Square and Round
Wrought-Iron Bars 52
Table of Weights per Linear Foot of Flat Wrought-
Iron Bars 53
MACHINE FORGINGSerial 1690 Edition 1
FORGING MACHINES
INTRODUCTION
1. In its broadest sense, machine forging is the working of
metal, either hot or cold, by means of a machine, causing it
to flow in such a way as to give it some desired shape, either
by slowly applied pressure or by blows. It is impossible to
exclude from this machine process of working metals anyforming operations on cold metals, as it has been found advan-
tageous to forge metals at temperatures varying from ordinary
atmospheric temperature to about 2,000° F. Low-carbon steel,
certain brass alloys, and altmiinum are frequently pressed,
rolled, or punched cold. Zinc is most easily worked at a
temperature of between 300° and 400° F, Aluminum can be
drop-forged at a temperature slightly below a dull red heat, but
it is very difficult to maintain it at exactly the required temper-
ature. Copper can be forged hot, and pure annealed copper
can be formed cold by pressing. From this it will be seen that
machine forging operations are exceedingly varied in their
nature.
Forging machines roll, hammer, or press the metal into the
desired shape, and most forging machines may use either plain
or formed dies. The use of formed dies will be considered
exclusively in this Section.
COPYRIGHTED BY INTERNATIONAL TEXTBOOK COMPANY. ALL RIGHTS RESCRVEO
§53
MACHINE FORGING § 53
ROLLS
2. Graded Rolling.—Work of varying thickness may be
done between properly shaped rolls. This is called gradedrolling, and is really forging with revolving dies. Graded
rolling is usually accomplished by passing a piece of metal
lengthwise between a pair of rolls, one or both of which are
more or less eccentric or have dies attached, so as to give the
finished piece a tapered form or a varying thickness. Silver,
German silver, and brass may be rolled by this method whencold; but iron and steel are usually rolled hot. In some cases,
the stock is simply passed through the rolls; that is, the piece
is placed against a guide, which serves to locate it properly
before starting through the rolls; the rolls then grip it and
carry it from the operator, requiring no further attention
from him. In other cases, dies are fastened to the rolls. These
dies do not extend all around the rolls, and when the parts
not covered by the dies are next to each other, an open space
is left between the rolls. The rolls turn continuously, and whenthe open space appears the work is
passed through it. As the rolls
turn, the dies come together, grip
the work, and roll it toward the
operator. The advantage of using
a machine in which the work is doneFig. 1
by rolling the material toward the
operator is that where several passes are required all work can
be done by one man, while with rolls carrying the work awayfrom the operator it is necessary to have a man at the back
of the machine to return the partly finished pieces. Graded
rolling is sometimes done to break down stock or to rough it to
shape, so that it may be finished by drop forging.
3. Some of the operations in the making of spoons are
excellent examples of graded rolling with dies. The blanks are
punched from a sheet j inch thick, in the form shown in Fig. 1
;
the piece a is waste, and b, c, d, e, f, and g are spoon blanks.
The large end of the spoon blank, which is to form the bowl,
§53 MACHINE FORGING
is first made wider by cross-rolling; this is done in some cases bypassing the blank sidewise between rolls about 6 or 8 inches in
diameter, the rolls being ^;>.^
located between housings,
as shown in Fig. 2. A part
of each roU is made smaller
in diameter, that is, it is
cut away so as to clear the
spoon handle, shown at b.
The portions r r of the rolls
do the cross-rolling; the
rolls are connected by suit-
able gears, which are placed
on the ends of the roll shafts.
In other cases, the cross-FiG. 2
roUing is done between overhanging rolls, as shown in Fig. 3;
these rolls are 10 or 12 inches in diameter, to insure the neces-
sary stiffness. The portions of the rolls between the housings
are frequently used for other work. Driving gears are located
on the ends of the roll shafts at the side g.
The tliickness of the metal varies in different parts of a
spoon and this varying thickness is produced by graded rolling.
Part of the circumference of the rolls is cut away so that the
-^ C^ length of the circimi-
ference remaining is
equal to the length
of the spoon. Thepart of the roll that is
not cut away is shaped
so as to produce the
desired taper on the
work. A different set
of rolls must therefore
be made for every size
or style of spoon. InFig. 3
some cases the work passes through the rolls away from the
operator and falls out on the other side, while in others it is
rolled toward the operator.
MACHINE FORGING 53
4. In rolling rifle barrels, steel billets are heated in a furnace
and then passed through successive grooves in a pair of special
eccentric or graded rolls, until the barrel is reduced to the
proper size and has the required taper. As the billet passes
through the first groove, it is seized by a helper at the back
and passed over to the workman in front. The work passes
between the rolls with the large end first, passing once through
each groove, except the last, through which it is passed twice;
the work is given a quarter turn between each two passes. As
Fig. 4
soon as the barrel is rolled to size, the ends are sawed off to the
proper length.
5. A pair of graded rolls fitted with dies for special forging
work, on either hot or cold metal, is shown in Fig. 4. These
rolls are provided with nuts and collars, between which the
rolling dies are clamped. The dies can be removed and changed
at will, so that a large variety of work can be done on one pair
of rolls. The rolls turn so that the work is run toward the
operator, and, as the dies do not extend over the entire
§ 53 MACHINE FORGING 5
circumference of the rolls, the metal is passed between themat the time in the revolution when the dies are out of the way.
The work is located by guides, which control its position both
vertically and horizontally. When rolling hot metals, the
location is determined by a stop a on the tongs, Figs. 4 and 5.
Fig. 5
It will be noticed that this is simply a clamp screwed to the
tongs; it is brought against a guide fastened to the front of
the rolls, to show how far the iron should be pushed in between
the roUs. Sometimes the end of the tongs strikes the guide, and
this serves to locate the work. After the work has been placed
in position, the revolving dies catch the piece and roll it toward
the operator. As soon as the dies leave the piece, the operator
puts it in position for a second pass through the rolls, either
giving it a quarter tiu*n and returning it through the same
groove, or giving it a quarter turn and placing it in the next
groove; in this way the work is continued until completed. In
the machine shown in the illustration, there are three grooves,
and the work is given two passes in the first groove, two in
the second, and three in the third groove.
6. In Fig. 6 is illustrated the back of the machine shownin Fig. 4. In this view, the dies a are clamped between the
nuts b and the coUars c on the other ends of the rolls. Thework d is shown in position ready for the dies to grip it as they
come around to the proper point ; the arrows show the direction
in which the rolls are turning. A peculiar arrangement of
gearing is used for driving these rolls, which admits of the
adjustment of the distances between the rolls; this is accom-
plished by driving the top roll by a train of three gears, one
being an idler swinging about one of the others and meshing
with both.
7. Screw-Thread Rolling.—Screw threads are rolled onwood screws, track bolts, machine screws, and manv other
6 MACHINE FORGING 53
screws and bolts, from small sizes up to 1^ inches in diameter.
The thread is formed by rolling the stock between suitable
dies, with sufficient pressure to force the material out of the
grooves to form the thread points. That is, the cold metal is
caused, by the pressure on the dies, to flow from the bottom
of the spaces and form the full thread. It is in reality a cold-
forging process.
8. Machines for rolling screw threads are made both
horizontal and vertical, but since the horizontal and vertical
machines are alike in principle only one will be described here.
Fig. 6
The front view of a vertical thread-rolling machine is given in
Fig. 7. There are two dies a and b;ais fastened to the frame of
the machine, and b is attached to a crosshead partly shown
at c. The blank that is to be threaded is placed on the feed bar d
and is introduced between the dies at the proper moment by the
pusher, or starter, e. To start the blank, the feed bar d is
automatically withdrawn from between the dies and the starter
moves forward, pushing the blank between the dies. Both the
feed bar and the starter are moved by the cam / on the driving
shaft. The crosshead c is moved through the connecting-rod g
53 MACHINE FORGING
and yoke hhy a crank on the shaft t. The shaft i is driven from
the pulley / by gearing of which k is part. The yoke h is
arranged so that, when the gear k turns in the direction of the
arrow, the crosshead is given a slow motion on the down, or
working, stroke and a quick motion onthe up, or idle, stroke. The back of
the crosshead c bears on a set of rollers,
Fig. 7
one of which is shown at /, and the working faces of the dies
are lubricated by oil that flows from the pipe m. The station-
ary die a is adjusted to roll a full thread by the wedge n and is
clamped in the final position by the bolts o.
8 MACHINE FORGING §53
Fig. S
9. The threads on the dies are laid off at an angle as shown
in Fig. 8, which is a die for forming a right-hand thread. Thelength of the die is
about three or four
times the circumfer-
ence of the blank so
that the screw will
turn around, between the dies, about that number of times in
forming the thread.
Screw threads are rolled on many small pieces, the material
being either hot or cold, depending on the size and character
of the article. The rolled thread is claimed to be muchstronger than a cut thread, but it is exceedingly difficult to
keep dies in shape for rolling threads on hot stock; hence, this
process is used mostl}^ for rolling threads cold.
Fig. 9 shows how the metal is displaced by the dies to form
the thread on the bolt a ; the dotted line b c shows how deep
the dies press into the stock, and also how the diameter is
increased on account of the thread. As the finished thread
must have a definite diameter, it is very important that the
stock used should be of the right size
;
if the stock is large the screw will be
too large, and if too small the screw
will either be too small or the threads ^will not be perfect. The size of stock
required to make a rolled thread of
any given diameter can be calculated,
but owing to the fact that the rule is
long and rather complicated, and that
the diameter of stock must sometimes
be changed after trial because the
metal will not always flow readily into
the points of the threads, a simpler
but less exact rule is ordinarily used.
The first trial size of stock is obtained by subtracting the depth
of the thread from its outside diameter. The depth of the
United States standard threads may be found by dividing .6495
by the number of threads per inch ; and the depth of V threads
Fig. 9
53 MACHINE FORGING
may be found by dividing .866 by the niimber of threads per
inch. The diameter of stock for some of the most commonsizes of rolled threads is given directly in Table I.
TABLE I
SIZE OF STOCK FOR ROLLED THREADS
Diameter
10 MACHINE FORGING 53
An example may be used to explain the determination of the
size of stock when it is not obtainable from Table I.
Example 1.—What size of stock should be used to make 12 rolled
United States standard threads per inch, f inch in diameter?
Solution.—Owing to the fact that a |-inch screw does not ordinarily
have 12 United States standard threads per inch, this combination does
not appear in Table I. It wiU therefore be necessary to calculate the
size of stock required to make these threads. According to the explanation
iust given, the depth of the thread is
.6495^12 = .054 in.
and the diameter of the stock is
.75 -.054 = .696 in. Ans.
It is sometimes required to find the diameter of thread that
will be produced by rolling a given number of threads per inch
on stock of a given size. In this case the depth of the thread
should be added to the diameter of the stock, the depth of the
thread being found as described in the foregoing example.
Example 2.—What outside diameter of thread will be produced by
rolling 10 V threads per inch on f inch stock?
Solution.—The depth of the V thread is
.866^10 = .0866 in.
and the outside diameter of the thread is
.75+ .0866 = .8366
which is practically .837 in. Ans.
11. Bending Rolls.—^Plates are bent in bending rolls,
which are placed as shown at a, b, and c, Fig. 10. Roll a is
arranged so that it can
bemoved toward or awayfrom b and c, in order to
give the plate d, that is
being rolled, the desired
curvature. The roll a is
called the bending roll
and rolls b and c are the
pinching rolls. The side
view of a set of bending
rolls is shown in Fig. 11, in which the rolls a are driven by elec-
tric motors c, thi'ough gears b, d, e, g, f, and shaft h. A gear / is
Fig. 10
§53 MACHINE FORGING 11
attached to each of the pinch-
ing rolls, both of which are
driven by gear g. The farther
motor also drives gear ethrough
gearing that is not shown, sim-
ilar to b and d. The pinching
rolls, which are driven, are also
called live rolls; and the bend-
ing roll, which is not driven, is
called a dead, or idle, roll.
12. The pinching rolls are
stiffened by supports / and
rollers n so they will not spring
down in the middle. Eachpinching roll has three slots mto help start the plates squarely
through the rolls. The plate
is put between the bending roll
and one of the pinching rolls;
then, as the roll rotates, the
edge of the plate is caught byone of the slots, bent up around
the bending roll and started
between it and the other
pinching roll. Cylindricalwork is removed from the rolls
by turning down the end i
with the bearing /, it being
hinged for that purpose, and
raising the roll by the rigging
shown at k. The curvature
of the plate may be controlled
by raising or lowering the
pinching roll. This is done
by a mechanism partly shownat the right of the supports /.
The two ends of the bending
12 MACHINE FORGING §53
roll may be moved together, or either end may be movedindependently of the other end. By moving one end of the
bending roll closer to the pinching rolls than the other, conical
work may be formed.
HAMMERS
13. steam Drop Hammer.—The steam drop hammerhas many of the advantages of other drop hammers and it
possesses one advantage not shared by them; that is, that
steam may be used for driving the piston down more rapidly.
Fig. 12
and hence an exceedingly quick and powerfiil blow can be
struck; or the piston may be let down slowly until the upper
die rests on the work, when the steam pressure is applied and
the dies forced together with a imiform pressure, as in the case
53 MACHINE FORGING 1 *>
of an ordinary power press. The work may then be finished
by one or two blows of the hammer; in other words, the steam
drop hammer is capable of a wider range of work than other
forms, but as a rule
it requires a somewhat
higher degree of skill
in the operator.
14. Steam DropPress. — There is a
large variety of work
that must be pressed
to bring it approxi-
mately to shape, and
then a few sharp blows
from a hammer must
be struck to finish it.
The steam drop press,
which closely resem-
bles the steam drop
hammer, has been
brought out to meet
this demand. Oneform of drop press is
showninFig. 12. Thelower die is held in
place on the base a
by the poppets b,
which extend through
the base and are se-
cured by keys below.
The head c that car-
ries the upper die, and
moves between the Fig. 13
guides d, d' , may be allowed to fall by gravity or may be forced
down by steam or air pressure acting on a piston in the cylinder
e. The lever / operates the piston valve in the valve chest ^,
and also moves the latch h out of the way when starting the head
14 MACHINE FORGING
from its highest position, where it is held by the latch when the
press is not running. This type of press is used for large thin
work, such as dish pans, where
the work is first pressed into
shape and then finished by two
or three quick blows.
15. strap and PulleyDropPress .—Inthe strap and
pulley drop hammer, shown in
Fig. 13, the weight is lifted by
pulling on a strap that passes
over a constantly rotating pul-
ley. The pulley b is kept rota-
ting by a belt on the pulley d,
and when the end of the strap
e is hanging loose the friction
on the pulley is not sufficient
to lift the weight. When the
operator brings pressure on the
strap, either by pushing his
foot down in the stirrup at c
or by gripping the strap higher
up with his hand and pulling
down, the friction of the strap
on the pulley b is increased to
such an extent that the ham-
mer head is lifted. When the
head reaches the desired eleva-
tion, the tension on the strap
is relieved, allowing it to slip
over the face of the pulley as
the head falls.
The poppets, shown at a,
are used to hold the lower die
in place. They are made with
long shanks that fit holes in the base of the hammer, and with
adjusting screws through the tops to locate and hold the die.
§ 53 MACHINE FORGING 15
16. Board Drop Hammer.—One of the most commonforms of drop hammer is known as the board drop hammer, one
form of which is illustrated in Fig. 14. The hammer head a
and board b, to which it is attached, rise and fall together.
Friction rolls c on each side of the board are attached to shafts
carrying pulleys d turning in opposite directions, and run bybelts in the directions shown by the arrows. The friction rolls
are thus run continuously in the directions required to raise
the board, but in their normal position they just clear the board.
The rod e operates a cam that moves the rollers c so that they
grip the board and raise it and the hammer. The foot
treadle h is connected by a strap g to the lever /, and is also
attached to the rod i, and thus operates the latch /.
17. When not in use, the hammer head is usually held upby the latch ;, which is placed at about the highest point from
which it is desired to have the hammer drop. When it is desired
to strike a blow, the treadle is depressed, which pulls out the
latch ;', and permits the outer end of the lever / to rise andthe rod e to fall. When the hammer falls, the lug on the hammerhead strikes the lower dog on the rod e, carrying the rod downand forcing the friction rolls c against the board. The hammeris then raised, the rolls remaining in contact until the hammerhead strikes the upper dog k on the rod e, thus raising the rod
and throwing the friction rolls out of contact with the board.
The hammer then again falls, striking another blow, and carry-
ing down the rod e and throwing the rolls into contact as before.
This process is repeated automatically, striking continuously,
until the treadle is released, and raised by the spring shown at
the right-hand side of the hammer ; then the latch ; again catches
the hammer head and holds it in the raised position. Light
blows may be struck by releasing the treadle at each rise of the
hammer before the hammer head strikes the dog k, throwing
out the friction rolls and causing the hammer to drop before it
has reached its full height. The operator can thus vary the
stroke as conditions may require. The hammer may be set for
different heights of drop by moving the latch / and the dog k
up or down.
Fig. 15 16
§ 53 MACHINE FORGING 17
18. Crailk Drop Hammer.—A common form of crank
drop hammer is shown in Fig. 15. In this type of hammer, the
hfting mechanism is arranged in such a manner as to rotate
the crank o, thus h'fting the hammer head b by means of the
ropes c, or by a leather strap. The mechanism is driven by a
belt on the pulley d, on the shaft carrying the pinion h that
drives the gear i. A clutch e is so constructed as to raise the
hammer after each stroke and hold it in its highest position
until the treadle / is depressed. The treadle / is connected,
through the rod g, to the clutch e. Bj^ keeping the treadle
depressed, the hammer will strike successive blows.
19. Advantages of Board and Crank Drop Hammers.Board and crank drop hammers have a number of points that
distinguish them from each other. In general, a board drop
hammer strikes a quicker or sharper blow for the same weight
of hammer head and same height of drop. The blow of the
board drop hammer may also be quickly regulated by varying
the height of the drop.
The crank-liji, rope-lift, or strap-lift drop hammer, as it is
variously known, is largely used for bending, shaping, straight-
ening, and welding. These hammers are used extensively by
the manufacturers of agriciiltural implements, and also by
malleable-iron companies. The crank machines have an
advantage in the lifting arrangement because the board drop
hammer depends on friction for lifting the hammer, while with
the crank drop hammer, the lifting is positive. The board and
gearing are expensive, so that a crank machine of a given
capacity and weight of drop will cost less than a board-operated
machine. The form of the lifting device is not of muchimportance in the case of light work, but for manufacturing
where large forming dies are used it is a point well worth
considering. As a rule, the crank machine is simpler and
requires less skill for its operation ; hence, it is preferred for rough
work. It is also used very extensively for forging soft metals
cold, as in making spoons, watch cases, and similar work.
In many classes of work, it is absolutely necessary that the
hammer head or drop should fall from two or more heights, in
18 MACHINE FORGING § 53
order to strike light or heavy blows when forging; and some-
times, as the work is turned from side to side, these light and
heavy blows must alternate. For such work the crank hammeris not suitable, and it is necessary to use a board drop hammer.Even for the lighter class of forgings, especially where the dies
are frequently changed, the board drop hammer is generally
considered the better.
20. Die Forgings.—Die forgings are produced in formed
dies that are shaped more or less closely to the outline of the
forging. Various machines, such as drop hammers, steam ham-mers, and presses, are used to force the stock into the dies. Adrop forging is a die forging that is produced by using the force
of a falling weight to drive the stock into the dies. Dropforgings may be produced on a drop hammer or a steam ham-mer. When a steam hammer is used, the force of the blow
struck by the falling hammer head may be increased by steam
pressure behind the piston. The general process of making die
forgings will be explained by means of a simple example requir-
ing but two operations and other forgings requiring these and
additional operations will be described later throughout the
remainder of this Section.
21. The clips used to hold the wooden and iron parts of a
wagon axle together are made flat, as shown in Fig. 16, and are
bent to fit the axle on which
they are to be used. Theends a and b are threaded to
receive nuts that hold a yoke
on the clip after it has been
bent. The fiat part is madevery thin, sometimes only
Y2 inch thick, so that it can be bent cold. Recesses in
the forging dies form the round ends a and b, and the
conical parts d and e that join them to the fiat part. Theforging dies are shown in Fig. 17, in which (a) is a view of the
face of the upper die, (6) is a section of the upper and lower
dies, showing the recess in which the forging is made, and (c) is
the face of the lower die. The top surface of the lower die in
Fig. 16
20 MACHINE FORGING § 53
view (b) is on the line ah c d eJ and the lower surface of the
upper die is at a g /i ij J. From k to i the upper die does not
touch the lower die, and the distance between the dies, when the
upper die is clear down, gives the thickness of the fiat part in
Fig. 16.
22. This forging is made from bar iron, which must be
large enough to fill the die at the largest part. There are
other parts of the die that such a bar more than fills and there
must therefore be some provision made for the disposal of the
excess metal where it can later be removed without injury to
the forging. This provision is made by leaving a shallow
recess k in Fig. 17 (a) and (c), called the flash, which makes a
narrow opening /, in (6), around the forging impression. Theexcess metal squeezed out into the flash around the forging is
called the fin and sometimes, also, the flash. Since these dies
do not come together between h and i, that is, the stufaces mand n do not come together, the fiat part of the forging can
spread out as much as necessary and no flash need be provided
for this part of the forging. The part of the bar that is not
needed for the forging, sticks out of the die through the sprue o.
The sprue is connected with the die impression by the gate p.
Fig. 18
23. The forging produced by the forging dies is shown in
Fig. 18 with the fin a still attached and the fiat part h is very
much larger than is required in the finished forging. Thefin a is removed by a punch and die, shown in Fig. 19 (a) and (6),
which also trim the fiat part h to the required size and shape.
The die, or trimmer, shown in (6), is made of two blocks a
and h in which an opening c has been cut. This opening is the
size and shape of the outline of the finished forging and it
extends clear through the trimmer. The punch d in view (a)
fits in the opening c in the trimmer, and its lower surface is
53 MACHINE FORGING 21
shaped to bear evenly on all parts of the forging. The rough
forging shown in Fig. 18 is laid on the trimmer, Fig. 19 (6), so
that the round ends rest in the parts e and/ of the opening and
the fin extends out over the surface of the trimmer. The
punch is then brought down on top of the forging, forcing it
through the trimmer, cutting the fin off and leaving it on the
surface of the trimmer. The fin must be cut from the end of
the bar from which the forging was made, so that it will not
interfere with the making of the next forging. The cut-o^ g
Fig. 19
is therefore fastened to the end of the punch so that it comes
into action over the shoulder k when the punch has nearly-
severed the forging from the fin. The cut-off must be wide
enough to reach clear across the fin and cut it entirely off.
The trimmer is made of two blocks, so that the opening c, when
it has been enlarged by wear, can be brought back to the required
size and shape. The shape of the opening in each block is first
trued up and the joints between the two blocks are then faced
off to make the opening of the right size.
22 MACHINE FORGING §53
24. It is not always possible to complete a forging in one
die, as was done in the case just described, and the forging dies
are then provided with two or more impressions, thus doing
the required work on the stock in a series of steps. The niimber
of blows that must be struck depends on a number of con-
ditions, but must always be enough to make the upper die strike
the lower die. The number of blows will be affected by such
conditions as the weight of the hammer, the height of the
drop, the size of the stock, the kind, quality, and. temperature
of the metal, and the depth and shape of the recesses in the
dies. In general, the heavier the hammer, the higher the drop,
the smaller, hotter, and softer the stock, and the shallower the
recesses in the dies, the fewer will be the number of blows
required to finish the forging.
25. Such articles as spades, shovels, scoops, conveyor
buckets, and wheelbarrow bodies may be formed in dies by
drop hammers. The lower die forms the outside and the upper
die the inside of the article. Some of these articles, such as
wheelbarrow bodies, are made in steam drop hammers. Theupper die is brought down against the stock, and steam is then
turned on, pressing the stock into the lower die, and a few light
blows are then struck to remove wrinkles and make the stock
fit the die closely. Shovels are
made under drop hammers. Theheated stock is placed over the
lower die and struck as many blows
! i ill as are needed to make it fit the die
closely. The dies with which scoop
shovels are formed are shown in
Fig. 20. The lower die, shown in
(a) , forms the outside of the shovel
and the inside is formed by the upper die, shown in (6) . The back
of each die block is planed smooth, so as to give a good bearing
on the bed or the head of the hammer. The lower die is held
in place by setscrews passing through poppets on the bed of
the hammer. The upper die is fastened to the hammer head
by bolts that pass through ears on the head, or by a dovetail
(a)
Fig. 20
§53 MACHINE FORGING 23
and key. Suitable stops are provided to facilitate placing the
upper die properly over the lower one.
26. Automobile front axles are frequently drop-forged, the
dies usually being long enough to forge half the length of the
Fig. 21
axle at a time. The order in which the operations are performed
and the details of some of the operations depend largely on the
design of the axle and the size of stock of which the axle is
being made. A front axle that is forged from square bar is
illustrated in Fig. 21. The bar is large enough to make the
body of the axle, but upsetting at a and b, as shown in Fig. 22,
is necessary, to make the forked end a and the spring pad b.
This operation is performed before the axle is taken to the forg-
ing hammer, in an upsetting machine, which will be described
later. The forging is done in two stages; the first is a
roughing operation which spreads the end preparatory to form-
ing the forked end. A steam hammer is shown in Fig. 23
fitted with the roughing dies for this axle. The upper die a
is keyed to the hammer head with a key b that is formed to fit
the space between the dovetail on the die and the side of the
slot in the hammer head. The lower die c is keyed to the anvil.
Two keys are used in this case, one driven from each end of
the die. When making the dies, one end and one side of the
Fig. 22
die block are first planed straight and square with the working
face of the die and with each other. The impressions in the
dies are then laid out so that they will come together when
these squared edges are in line with each other. The squared
ends are lined by moving one or the other die backward or
24 MACHINE FORGING 53
forward as may be required. The sides are lined by movingthe hammer frame sidewise on the anvil block. This moves the
upper die crosswise, but
does not change the
position of the lower
die. When the dies
are properly lined, the
hammer frame is fast-
ened down by anchor
bolts d. Heavy springs
are placed under the
nuts on the anchor bolts
so that when such a
heavy blow is struck
that there is danger of
breaking the hammer,
the hammer is lifted
slightly from the anvil
block.
27. Considerablescale forms on the mate-
rial that is heated for
forging, and some of it
when loosened by the
forging operation drops
into the lower die. If
the scale were allowed
. to stay in the die, the
^ forging would be rough
and not true to the die.
A blast of air from the
blast pipe e is therefore
directed on the lower
die to keep it free from
scale. The dies are long
enough to forge slightly
Fig. 23 morethan halfthe length
§53 MACHINE FORGING 25
of the axle, so one end of the axle is heated and forged and then
allowed to cool. The other end is then heated and forged in the
same way. In order to facilitate the forging operation, the
finishing dies are set up on a hammer beside the first one so
that, when one end has been rough forged, it is taken to the
finishing hammer and finished with the one heat, and the fin is
trimmed in a trimming press. In this way each end is com-
pletely forged and trimmed with one heat. The axle is forged
straight, and is bent to the required form on a press.
28. A large axle of somewhat different design from the one
shown in Fig. 21 is illustrated in Fig. 24. This axle is heavier
at the middle than at the ends and it is therefore not possible
to use stock large enough to fill this part of the die without
leaving an excessively large fin at other parts of the forging.
Stock that is larger than is required by the part of the forging
at a, but not quite
large enough for that
at h or at c, is therefore
used. The forging of
each half of this axle
is completed in foiu"
operations with two
dies. The operations
are fulling, breaking
down, roughing, andfinishing. The first
three operations are performed under a roughing die and the
fourth operation under a finishing die.
29. The lower roughing die is illustrated in Fig. 25. ThefiiUer, shown at a, throws the metal both ways, into the spaces h
and c. The metal in h provides stock for the formation of the
Fig. 25
26 MACHINE FORGING 53
axle end, and that in c provides stock for the heavier portion
of the axle body. The stock is then bent in the breakdown d
so that it will lie over the roughing impression. The upper
roughing die is like the one shown, excepting that the break-
down projects from the face of the die block instead of being
cut into it. After the stock is bent, it is roughed out in the
impression e. The projection in the center of this die gradually
tapers out at / so as to throw the surplus metal toward the
middle of the axle where it will be needed in the finishing oper-
ation. The finishing impression is shown in Fig. 26. The other
die of this pair is
like the one shown.
The impressionbrings the forging to
size and a flash a is
provided to take the
excess metal that is
squeezed out. These
dies, like those for
the other axle, forge half the axle at a time. Such dies as these
are rather hea\^ and must therefore be lifted by a crane. In
order to facilitate the lifting of the dies, holes b are drilled in
the ends of the die block, and steel pins, over which the crane
chain is fastened, are stuck into these holes.
Fig. 26
30. Drop-Hamixier Foundations.—^As it takes some
appreciable time for the blow to penetrate to the center of a
piece of metal, drop hammers are sometimes provided with an
elastic foundation. The elasticity has the effect of distributing
the force of the blow over a longer period of time, thus causing
it to penetrate deeper. Such a foundation is usually made of
large timbers, carefully squared and made to fit each other
quite accurately, as shown in Fig. 27. The anvil a is then placed
on the foundation, usually with a layer of leather belting or a
rubber pad between the top of the timber and the base of the
anvil. The bottom of the timbers h should be bedded in con-
crete to insure an even bearing. The objection to the all-
timber fotmdation is its great cost and renewal expense.
53 MACHINE FORGING 27
31. Elastic foundations have been made by placing the
timbers for the foundation in a vertical position. A log large
enough in diameter to receive the anvil on its top and to enter
the ground 6 or 8 feet is sometimes preferred. The hole is
dug 1 foot deeper than is necessary to receive the log. A foot
of concrete is then placed in the bottom of the hole, andthe log bedded, in a perpendicular position, on top of this.
For light drop hammers, a large flat stone is sometimes placed
under the bottom of the log. The space about the log in the
hole should be filled with earth well tamped into place; the
top of the log should be trim-
med off to a true horizontal
siu-face. In the case of ham-mers with openings in the
center of the anvil, it is
necessary to cut a depression
in the center of the top of the
log, with a groove leading to
the outside to allow scale
and dirt to pass off without
accumulating under the
anvil. When a log large
enough for the anvil cannot
be obtained, several timbers
may be bolted together to
form a block of sufficient size.
Chestnut or oak timbers are
said to be the best for drop-hammer foundations. For hammerswith drops weighing 1,000 pounds or more, a masonry foundation
is recommended by some builders. A hole is first dug 10 to 14
feet deep, and the masonry built up to within 4 feet of the top.
On top of the masonry, oak timbers 4 feet long standing on
end are arranged, and bolted closely together. The space
around the timbers is then filled with concrete; the anvil is set
on top of the oak timbers, as in the case of the foundations
already mentioned. In some cases, masonry foundations are
built up to within an inch or so of the anvil, and a thick
rubber or leather pad placed under the anvil.
Fig. 27
28 MACHINE FORGING 53
32. One manufacturer of drop hammers recommends the
soHd foundation shown in Fig. 28. It is made by digging a
hole of the required depth, and Hning it with planks, as shown.
The space inside of the planks is then filled with concrete.
The following proportions for the composition of the concrete
are recommended : three barrels of stone, two barrels of gravel,
1^-^__- and one barrel of cement.
\ ? /flTable II shows the dimen-
sions of the foundations for
various weights of the drop,
generally called the weight
of the hammer.
The dimensions for the
foundation of any hammerare found in the same hori-
zontal line as the weight;
Fig. 28
the letters at the head of the columns correspond to those in
Fig. 28. Foundations of this kind have been built without
using any elastic material between the anvil and the concrete,
with very satisfactory results.
Concrete foundations may be strengthened with reinforcing
rods, as shown at o, when it Is thought the concrete does not
supply sufficient strength.
30 MACHINE FORGING § 53
33. Comparison of Drop-Hammer Foundations.—It
has been found in practice that when the anvils of large ham-mers are light, it is necessary to use elastic foiuidations or the
force of the blows will cause the foundations to yield. In the
case of a large steam hammer installed by the Bethlehem Steel
Company, the first foundation, which was made of timber, hadvery little elasticity. This foundation yielded so that it hadto be rebuilt. The second foundation was made very elastic
by placing wood shavings and brush beneath the timbers, and
no further trouble was experienced.
If the anvil is made heavy enough, it will not have time to
move away from the work before the hammer has exerted
its full effect, and hence an elastic foundation would not relieve
the shock of the blow. With a relatively light anvil, the spring
of an elastic foundation allows the anvil to recede when the
blow is delivered, and thus prolongs the action of the blow;
but it is only on large work that it is especially desirable to
obtain this effect.
34. It has been found that a hammer having a solid founda-
tion of sufficient size will do as good work as one having an
elastic foundation and dropping about twice as far. Theshorter drop also allows the hammer to strike more blows per
minute than when operating with a higher drop. Hence, a
greater amount of work can be tiimed out.
It has been found also that when the solid foundation is used
practically no repairs are necessary, and a much greater niimber
of hours of work can be done, per year, by a given hammer.
It is an interesting fact that wherever the solid foundations
have been adopted, and the height of the drops properly
adjusted, their use has not been abandoned.
Foundations for steam hammers are usually proportioned to
suit the condition of the ground on which the hammer is to be
installed. Any foimdation dimensions that might be given
would therefore be of but limited application.
53 MACHINE FORGING 31
SWAGING MACHINES35. Swaging is a cold-forging operation that is performed
by pressure applied, removed, and applied again, in rapid
succession. At the speeds ordinarily recommended by swaging-
machine manufacturers, pressure is applied from 2,000 to 6,000
times a minute, which is almost equivalent to a continuous
pressure and causes the metal to flow into the new form. Thework done by a swaging machine is round or conical in shape,
such as the pointing
of pins, the tapering
of tubing for bicycle
forks, the reduction
to exact size of parts
of forgings that are
to be threaded, etc.
The front of a
swaging machine is
shown in Fig. 29. Thecentral part a revolves
when the machine is
in operation, and the
stock that is to be
swaged is put into the
opening b. The out-
side ring c is attached
to the standard d and
therefore remains sta-
tionary. The rotating
head a is on the end
of a hollow shaft which
carries the flywheel e on the other end. A similar machine is
shown in Fig. 30 (a), with the ring /and the guards g and h
shown in Fig. 29 removed to show the working parts.
The rollers a are supported by the ring b around the rotating
head c. There is a slot running across the center of the revolv-
ing head c, view (b), and two dies d and the backers e are
fitted into this slot. The dies and backers are free to slide
Fig. 29
32 MACHINE FORGING 53
back and forth in the slot and tend to move outwards
when the machine is running, but when the backer passes a
roller, the die is forced in against the stock. The face of the
:^ (a) C
Fig. 30
dies may be flat or they may have recesses the size and shape
of the part that is being swaged.
PRESSES
36. Presses are used for forming or shaping metal, for
punching holes, and for trimming the fins from drop forgings.
One common form of press, shown in Fig. 31, is driven by a
belt on pulley a, which drives the gear b continuously. Bydepressing the treadle d, the clutch c is thrown into action and
the head e is driven down by the eccentric /. The upper die is
attached to the lower face of the head e, and the lower die is
carried on a block h that fits over the opening g. In order to
adjust the height of the dies to suit the work, an adjusting
nut is provided at /.
Work that is too heavy for an open-sided press, such as that
shown in Fig. 31, may be done on a double-sided press, such as
the one illustrated in Fig. 32. This form of press is frequently
used to trim the fin from drop forgings and it is for that reason
commonly called a trimming press. When trimming small
53 MACHINE FORGING 33
forgings cold, the forgings are usually punched through the trim-
ming die, which is fastened to the bed of the machine, and fall
to the floor. When a small forging is trimmed while hot, the
fin is frequently left on the bar from which the forging wasmade. After the trimming is done, the gate is cut with the
side shear a. The height of the ram may be adjusted by the
nut b and the height
of the upper shear
blade by the nut c.
37. In the form of
press shown in Fig. 31
the finished work
passes out of the wayby falling through the
opening g, to the floor;
unlesssomesuchmeans
is provided the work
must be removed from
the diesby hand. Theinclined press shown
in Fig. 33 has been
found convenient for
discharging the fin-
ished work. The table
a can be set at any de-
sired angle by adjust-
ing the nut b. Thestock is passed into
the machine from the
front, and the finished
work slidesout through
the opening c at the back and drops behind the machine. In
other respects this press is similar to the one already shown.
38. P*ress Work.—Three operations are performed by
presses on the axle the forging of which was described in
Arts. 26 and 27; they are, in the order in which they are
performed, trimming, stretching, and bending. The stretching
Fig. 31
34 MACHINE FORGING 53
and bending will, however, be described first and the trimming
later. The stretching and bending are done in a press with a
two-part fixture. The forging operation does not always makethe axle the right length, and the center of the forging is there-
fore reheated and stretched as may be needed. The principle
of the fixtiire that does the stretching and bending is shown in
Fig. 32 Fig. 33
Fig. 34. Views (a), (b), and (c) show respectively the top, end,
and one side of the fixture, and view (d) shows the other side.
The stretching part of the fixture is shown in the lower part of
view (a), at the right of (b) and in (c). The base a is fastened
to the bed of the press and it carries two slides b working in a
dovetailed slot in the base a. The axle is put in the fixture as
shown at c, the slides b are sho^^ed together until the forked
E
s
<S5
d
s
35
5G MACHINE FORGING 53
ends drop between the stops d and the shoulders e, and the axle is
then clamped in place. The clamping is done by a wedge /and a key g at each end. The wedge/ is first laid in the channel
of the axle and the key g is then driven in over it. This locks
the axle in place. The axle is stretched by the wedge h whichis fastened to the ram of the press. As the ram descends, the
wedge h is forced down between the rollers i and the slides h
are moved apart, thus stretching the axle. The length of the
axle, when stretched, depends on the position of the ram with
respect to the fixture when at the bottom of its stroke, and this
is adjusted by means of the
adjusting nut on the ram h,
Fig. 32.
When the axle has been
stretched, it is removed andput in the bending fixture
shown at the top of view
(a) , the left of view (6) , and
in view {d). The axle is
placed against the stop /
between the guides k, which
hold it edgewise but do not
clamp it, and the upper die
/, which is fastened to the
ram and forces the axle
down into the lower die m.Fig. 35
39, The trimming of the axles shown in Figs. 21 and 24differs only in the shape of the trimming dies. The die shownin Fig. 35 is for trimming the axle shown in Fig. 24. Thetrimming die, Fig. 35 (a), is fastened to the bed of the press
and the punch, view (6), is fastened to the ram. The body of
the trimming die is box shaped, so that the axle falls downinside of it and is withdrawn endwise when the fin has beensheared off by the downward motion of the punch. Thepunch is shaped so as to bear as evenly as possible on all parts
of the forging in order that it may not be sprung when it is
pushed through the die.
53 MACHINE FORGING 37
Trimming of large forgings is usually done while they are
hot, and the trimming press is therefore set near the hammer in
which the forging is finished. The shearing plates a of the die
are made separate from the body, which may therefore be made
of a cheaper material than is required in the shearing plates.
The setscrews b hold the cutting edges against the forging so
that the fin is trimmed off smoothly, and the screws c lock the
shearing plates securely in position.
UPSETTING MACHINE
40. Upsetting machines are variously called forging
machines, bolt-heading machines, collaring machines, etc., depend-
ing on the operation that the particular machine is especially
Fig. 36
adapted to perform. The manner in which the forging is done
is, however, always the same. When the hot stock is placed in
the machine, it is gripped between two dies, one of which is
38 MACHINE FORGING §53
stationary, which hold it in front of a third die, or plunger
tool, that is moved endwise against the stock and forces it
into suitable recesses in the gripping dies and the plunger tool.
The gripping dies do not always hold the stock securely enough
to resist the thrust of the plunger, so it is frequently necessary
to provide a back stop of some kind to take the thrust of the
plunger. The form of this stop varies with the size and length
of the work that is being handled.
An upsetting machine is shown in Fig. 36. The stationary
die a fits in a suitable recess in the frame of the machine and is
held in place by the clamp b and setscrew c. The die a is in this
case small, so metal blocks are placed on top of it to give the
setscrew c a bearing. The outer gripping die, not shown, fits
in a recess in a movable head, and is held in place in the head
by the clamp d and setscrew e. When the machine is in oper-
ation, the movable gripping die is brought against the sta-
tionary die a, thus gripping the stock in the recess that is madefor it. The plunger / carries a die, or tool, that is called a
heading tool, upsetting tool, collaring die, etc., depending on
the kind of work that is being done. For the sake of sim-
plicity, this die will be called the plunger tool regardless of the
kind of work that is being done. The plunger tool is down on
a level with the die a and is therefore hidden by the comer of
the frame. The tool is, however, fastened to the ram / by
bolts g. The gripping die and the ram are
set in motion by depressing a treadle that
moves an operating mechanism through the
rods h and i. The holes shown at / are for
bolts that secure the back stop, which hasFig. 37 been removed from this machine. The dies
are cooled, when the machine is in operation, by streams of
water from the pipes k. The water striking the hot stock also
tends to loosen the scale and thus produces a smoother forging
than would be obtained otherwise.
41. Upsetting-Machine Work.—The clip shown in
Fig. 37 is made in closed dies so that no back stop is needed.
The dies for this piece are shown in Fig. 38, in which a is the
53 MACHINE FORGING 39
stationary die, b the gripping die, and c is the plunger tool. The
stock of which this clip is made is a rectangular block which is
placed, while hot, on the shelf d on the stationary die and the
Fig. 38
machine is set in operation. When the gripping die closes on
the stationary die, the part of the shelf d that projects from the
face of the die block fits into the lower part of the opening in
the gripping die. The advance of the plunger tool forces the
Fig. 39
metal to flow back into the space e and along the top and bottom
of the projection/ until it strikes the shoulders g. If the metal
strikes the shoulder g before the plunger has reached the end of
40 MACHINE FORGING 53
its stroke, the excess metal is forced up into the vent hole h and
is later cut off. The gripping dies a and b therefore form the
outside of the clip and the plunger tool c forms the inside of
the forked part and the rounded ends at a in Fig. 37.
42. The forked end of a locomotive side rod, shown in
Fig. 39 (a), is made in an upsetting machine. There are two
impressions in the gripping dies and two plunger tools are used.
The lower plunger tool is essentially a hot chisel, as it merely
splits the end of the rod and prepares it for the forming die
wliich is used afterwards. The stock for the side rod is rec-
tangular in shape and requires no preliminary upsetting. The
Fig. 40
gripping dies are shown in Fig. 40. The roughing, or splitting,
impression is shown at a. The depth of the impression at
the left end of the die is half the thickness of the main part of
the rod. Near the right end of the die the depth of the impres-
sion gradually increases until it is equal to half the thickness
of the forked part of the rod. The plunger tool with which the
end of the rod is split is shown in Fig. 39 (6). The width
at a 6 is approximately equal to the width of the slot that is
to be m.ade in the end of the side rod, and the length of the die
from c to <i is approximately the same as the depth of the
fork in the end of the rod.
§53 MACHINE FORGING 41
43. When the rod end has been spHt in the impression a,
Fig. 40, it is transferred to the upper impression b, where the
forked end is brought to the finished size and form shown in
Fig. 39 (a). The plunger tool for finishing the rod end is shown
Fig. 41
in Fig. 39 (c) . This die forms the inside a of the fork, view (a)
,
and the rounded end bed, all other parts of the rod end being
formed by the gripping dies. When the stock is taken from the
lower impression in the gripping dies, the end that has been
split is the same depth as the body of the rod, as shown in
view (d), so the plunger tool, view (c), not only forms the inside
of the fork but it also upsets it so as to form the enlargements
at b and d, view (a) . A back stop must be used with these dies
to keep the stock from being pushed out of the gripping dies by
the thrust of the plunger.
44. The dies with which the collar and spindle on the end of
an ordinary truck axle are formed are shown in Fig. 41. Thegripping dies a and b are rectangular blocks with an impression
cut in each of two opposite faces. I'hese impressions are
usually alike, so that when one impression becomes worn or
damaged, the die may be turned over and the other impression
may be used in its
place. The axle is
made of square stock
which is placed in the
recess of the station-
ary gripping die,
where it is held by
the moving die. The gripping dies really do little morethan hold the stock in line with the plunger tool which is
shown at c, so a back stop takes the thrust of the plunger.
42 MACHINE FORGING 53
The conical spindle, shown at a in Fig. 42, and the part of the
collar at the right of the line b c, are forged in the recess d of
the pltinger tool, and the part of the collar at the left of the
line 6 c is forged in the recess e, Fig. 41, in the gripping dies.
A vent hole is drilled in the side of the plunger die at the bottom
of the conical hole that forms the spindle. This vent provides
an outlet for the air and steam in the die as it is forced over the
hot end of the axle. These dies are water-cooled, and water
that gets into the plunger die forms steam when the die is forced
over the hot end of the axle.
PUNCHES AND SHEAHS
45. Punches may be used to make holes in sheet metal,
when the holes are not required to be of imiform diameter
throughout, or when they can be reamed to the desired size
after piuiching. Shears are used to cut bars or to trim plates
to the required size. Alligator, or lever, shears, such as shown
in Fig. 43, are especially useful for cutting bar, strap, and scrap
Fig. 43
stock. The stock is cut off between the shear blades a, b, the
lower one of which is stationary and the other attached to
the short end of the lever c, the long end being moved by a crank
or cam. In the shear shown, two flywheels d are placed on the
main driving shaft, so that their inertia will assist in operating
the shear and enable it to cut heavier stock; also, the bar will
§ 53 MACHINE FORGING 43
be gripped on one edge first, and the cutting will proceed from
one side to the other. This enables the shear to cut muchlarger stock than would be possible if the cutting edges of the
blades were to strike both sides of the bar along the entire width.
46. For cutting bars, narrow plates, etc., the shear shown in
Fig. 44 is quite frequently used. One advantage of this type is
Fig. 44
that it takes up less room than the lever shear. The shear
blades a, b are arranged much as in the lever shear, except that
the moving blade b is attached to a head, or ram, that descends
in a straight line instead of working about a pivot, as in the
lever shear. It will be noticed that the blade b is set at anangle to the blade a, so as to cause the cutting to proceed from
44 MACHINE FORGING 53
one side to the other and make it possible to cut off largei
stock. This is known as giving the blades sliear.
The operating parts are so arranged that when the treadle c
is released, the head with the blade h always returns to the
top of the stroke and remains in that position while the shear
is out of use. The pressure of the foot on the treadle c throws
Fig. 45
in the clutch d, connecting the head with the driving mechanism
and causing the shear to descend and continue to operate until
the treadle is released. This shear is also provided with a
flywheel e, to increase the effectiveness of the machine by
storing up energy between cuts and giving it up to the shear
when cutting. Sometimes the shear blades a, b are turned at
right angles to the position shown in Fig. 44. This is usually
§53 MACHINE FORGING 45
done with shears intended for trimming the edges of wide
plates. Special shears are also made for cutting off structiiral
or rolled shapes.
47. The shears shown in Figs. 43 and 44 cannot be used to
make curved cuts nor to cut wide plates, excepting that the
shear shown in Fig. 44 may be used to trim the edges of a plate
when the blades are set at right angles to the position shown.
Such a shear is sometimes called a trimming shear. The rotary
shear shown in Fig. 45 will cut ciuves in plates of any width,
but it will not cut angles, channels, or similar shapes. Thecutters a are shaped to cut perpendicular to the surface of the
Fig. 46
sheet, but other cutters that will produce an angle cut may be
used in their place. The lower cutter is driven by the pulley h,
through gearing inside the base, and a clutch operated by the
lever c. The lower cutter therefore driv^es the plate that is
being sheared, and for this reason it is slightly knurled. Whena plate is being cut, the part of the plate on the right of the
cutter passes through the opening shown at d, and that on the
left through the space e.
48. The shear shown in Fig. 44 is sometimes made conver-
tible, the shear and shear blocks being removable so that a
punch-and-die set can be substituted for the shears. Theattachments for a shear set are shown in Fig. 46, the assembled
46 MACHINE FORGING 53
parts being shown in (a) and the separate parts in (b). Theshear blocks a and b are bolted to the lower jaw and to the
ram of the machine, respectively, and the shear blades c and d
are bolted to the shear blocks.
The attachments for the ptmch set are shown in Fig. 47,
the parts being shown assembled in (a) and separate in (b).
The punch a is first attached to the punch stock b by the
coupling nut c. The punch passes through a hole in the coup-
ling nut which holds the head d against the end of the punch
stock. The die set is then assembled by placing the die e in the
Fig. 47
hole / of the die holder g where it is held by the setscrew h.
The die and die holder are then fastened in the die block i
by the setscrews /. When the punch stock b has been inserted
in the plunger, the die block is bolted to the lower jaw of the
machine. In order that the die may be brought in line with the
punch, the bolt holes k are made slightly elongated to permit
adjustment forward and backward. Adjustment sidewise is
obtained by means of the setscrews /. The stripper / is fastened
to the frame of the machine, with the semicircular opening ni
around the punch just above the plate that is being punched,
and pushes the work off the punch as the plunger rises.
§ 53 MACHINE FORGING 47
RIVETING MACHINES
49. Some riveting machines form the heads on the rivets
by a steady pressure, while others form the rivet head bystriking a series of rapid blows. The machine that forms the
rivet head by a steady pressure is comparatively large and is
therefore especially well adapted to riveting in a shop in which
much riveting is done, whereas the riveting hammer, that forms
the rivet head by a series of blows, is usually small and is
consequently used for riveting that is done away from a shop,
or in shops where a comparatively small number of rivets are
to be driven and the expense of the larger machine is not
warranted. A riveting hammer is shown in Fig. 48. Air at a
pressure of about 100 pounds per square inch is brought to the
hammer through a rubber hose that is attached to the handle a
Fig. 48
of the hammer at b and the operation of the hammer is con-
trolled by a valve that is operated by the latch c. The rivet
set d is cupped out to form the rivet head. The plunger strikes
from 800 to 1,100 blows per minute.
50. The riveter shown in Fig. 49 is larger than the one just
described. It is intended to be carried around by a crane, but
this form of riveter is also made to remain stationary. Therivet head is formed by the steady pressure of air or steam in
the cylinder a on the plunger b. The pressure is transmitted
to the movable rivet set c by a system of levers partly shownat d. The parts of the riveter are so proportioned that the
movable rivet set moves a considerable distance diuing the
first half of the plunger stroke but it cannot be made to exert
a very great pressure on the work during this part of the stroke.
48 MACHINE FORGING § 53
During the second half of the plunger stroke, however, the
movable set does not move very far but it can exert practically
the full pressiire for which the riveter is designed. In order
that the riveter may head rivets of different lengths and finish
the head during the last half of the plunger stroke, the rivet
set c may be adjusted to different heights. The gauge e has two
marks showing the position of the end of the plunger at the
Fig. 49
beginning and at the end of the second half of its stroke. These
marks enable the operator to adjust the upper set c so that the
riv^et head is completed during the second half of the plunger
stroke when the machine is able to exert its greatest pressure.
51. Riveting.—Rivets in structural work do not, as a rule,
have to be driven as hard as when they are to resist steam
pressure and hold the joint steam-tight. Some rivets maytherefore be driven sufficiently hard while cold to satisfy the
§53 MACHINE FORGING 49
conditions for structural work, but when the joint must be
steam-tight it is seldom possible to drive the rivets cold. Thepressure required to drive rivets of different sizes depends some-
what on the material of which the rivets are made. A machine
capable of exerting the pressure given opposite any given size of
rivet in Table III should have sufficient capacity to drive that
size of rivet.
TABLE mPRESSURES REQUIRED TO DRIVE RIVETS
Diameter of Rivets, in Inches
50 MACHINE FORGING 53
the diameter of the hole and the kind of a head that is to be
made. For the button head, the length of stock required for
the head is Ij times the diameter of the hole; for the point, or
steeple, head, the stock is about 1.3 times the diameter of the
hole; for the countersunk head, .8 times the diameter of the hole.
BUIiLDOZER
52. The bulldozer is a horizontal press for performing bend-
ing, forging, and welding operations. One of the most com-
mon forms is shown in Fig. 50. In the illustration, a pair of
dies a, b is shown in position for bending the piece of work /.
The moveable die b is attached to the ram d, which is driven bythe connecting-rods c.
These machines are
made to be driven by
a belt, engine, or elec-
tric motor, and are
used for a very large
variety of work, espe-
cially for such work
as the forgings for car
trucks, for agricultural
implements, etc. Analmost endless variety
^^^- 50 of work can be doneon them, including forging and welding. The stock is generally
put in the dies hot, and in most cases simple dies similar to
those shown in Fig. 50 are used.
53. Bulldozer Work.—The U-shaped strap shown in
Fig. 51 may be formed on a biilldozer. The straight stock is
first cut to length and the holes a, b, and c are punched some-
what smaller than the finished size. Holes a and c are then
reamed to size, but hole b is left the punched size, so that it can
be used in the bending operation. When the strap has been
bent into the shape shown, the holes a and c must be opposite
53 MACHINE FORGING 51
each other. Hole b is half way between a and c before the
stock is bent, and it therefore serves to center the stock while
it is being bent. The bending punch,
Fig. 52 (a), is bolted to the head of
the bulldozer and fits into the bend-
ing die, Fig. 52 (6) , which is bolted to
the table of the bulldozer. The body
a of the punch is an iron casting to
which the steel wearing plate b is
fastened. The steel dowel-pin c fits
into the hole b, Fig. 51, in the stock
and centers it so that holes a and c
will come opposite each other. Thebending die, Fig. 52 (6) is also an
iron casting. The opening d, into
which the stock is pushed for bending,
does not need to be as deep as the
piece that is being bent. It need only
be deep enough to make the stock
that is being bent lie close to the side of the punch
is a considerable force tending to drive the parts
Fig. 51
There
e and Japart when the die is in use, and these parts are therefore
Fig. 52
strengthened by ribs g and by the tie-bolt h. The tie-bolt is
placed high enough to allow the punch to pass under it.
MACHINE FORGINGSerial 1690 Edition 1
EXAMINATION QUESTIONS
(1) What is meant by machine forging in its broadest sense?
(2) How is graded rolling usually accomplished?
(3) What is the advantage of having the work move toward
the operator when rolling between dies?
(4) How are threads formed by the rolling process?
(5) What size of stock would be selected to make a United
States standard screw thread 1 inch in diameter by the rolling
process?
(6) What adjustment is made to form conical work on
bending rolls?
(7) What special advantage has the steam drop hammerover other drop hammers?
(8) Give one advantage of the board drop hammer over
the crank drop hammer.
(9) What is a drop forging?
(10) What is meant by the flash?
(11) How is the fin removed from the forging?
(12) What are two advantages claimed for a solid foundation
over an elastic foundation for a drop hammer?
(13) What is meant by swaging?
(14) What is the object of inclining the bed of a press?
§53
2 MACHINE FORGING §53
(15) What is the advantage of the vertical shear over the
lever shear?
(16) What is the object of setting one of the blades of a
pair of shears at an angle to the other?
(17) What is meant by a convertible shear?
(18) What two kinds of machines are used to form heads
on rivets?
(19) On what kind of work are hot rivets generally driven?
(20) What is a bulldozer?
FORGING DIESSerial 1682 Edition 1
FORMS OF FORGING DIES
DROP-FORGING DIES
PRINCIPLES OF DROP FORGING
1. The object of this Section is to explain the forms of
forging dies in use and the methods of making them. A dropforging is one made between dies by a machine employing the
force of a dropped weight. By the use of drop-forging dies it
is possible to make forgings that would otherwise be impractical
owing to the great expense. Drop forgings are made of any
weight from a fraction of an ounce to over a hundred pounds,
and forgings uniform in quality are produced in large quantities.
The advantages of drop forgings are low cost; uniformity, per-
mitting them to be used interchangeably; strength; ductility;
and a pleasing general appearance. Drop forgings are gen-
erally made of low-carbon steel, although they are also madeof alloy steel, wrought iron, tool steel, copper, and bronze.
2. Classes of Drop-Forging Dies.—One of the simplest
sets of drop-forging dies is shown in Fig. 1. It consists of the
upper die a, which is secured to the hammer, and the lower
die b, which is secured to the anvil. The recesses in the dies
are indicated by the dotted lines c. The die recesses are gener-
ally spoken of as impressions It will be noticed that the deeper
impression is in the upper die. This is generally so, owing to
£OPYRiaHT£D BY INTliR NATIONAL TEXTBOOK COMPANY. ALL RIGHTS RESERVED
§54
FORGING DIES §54
I z
XFig. 1
the fact that in practice it has been found that the metal then
more readily fills the impression in all parts. The line d, where
the upper and lower dies come
together, is known as the joint
line of the dies. The form of
the joint line depends on the
shape of the work to be made.
Drop-forging dies may be di-
vided into two classes: those
having a straight joint line as
d, Fig. 1, and those whose joint
line consists of two or more
straight lines that lie at an
angle to each other, or a com.-
bination of straight lines or
curves. It is essential that
there be little or no side thrust
from the dies to the hammer guides when in action; that is, the
dies should be balanced. This is readily done in the case of those
dies having a straight joint
line by making the dies so
that the joint will be at right
angles to the center line of
the hammer; that is, making
the joint line horizontal.
Dies of the second class
may be subdivided into those
in which the side thrust is
balanced by choosing a suit-
able angle for the lay of the
work in the die, and those in
which the thrust is balanced
by the addition of a part to
the die for this purpose.
3. In Fig. 2 is shown a^'""-^
pair of dies for a right-angle bend, in which the thrust is
balanced by choosing a suitable angle for the lay of the work.
54 FORGING DIES
In this case, the thrust in the direction a is offset by a thrust 6,
as shown by the arrows. The amount of the thrust in either
direction may be changed by changing the angles of the die. In
case the angles c and d were equal, the thrust would be awayfrom the side b which has the largest area. As the greatest
thrust occurs during the first few blows, the lay should be
made so the thrust will be balanced at that time. In the
figure, the dotted lines e represent the depressions in the dies
and the line/ is the joint line.
In Fig. 3, a pair of dies is shown in which the thrust is balanced
by making the dies so that the part a will back into the
part h and create an equal
thrust in the opposite direc-
tion. As before, the depres-
sioQS in the dies are indicated
by dotted lines c.
The surface of the dies that
meet when a blow is struck
is known as the striking
surface. Dies should be so
made that the striking sur-
face will be uniform around
the impressions.
5 Z
Z IFig. 3
4. Die Parts.—It is only
in the case of the simplest
forgings that the work maybe finished in a single die recess. Four recesses may be neces-
sary, the fuller; the breakdown, bending impression, edger, or side
cut; the roughing impression; and the finishing impression. Tothese may be added the cut-off in case the forgings are to be cold-
trimmed. Some parts of the finished forging are thicker than
others, and, as the work is forged from a bar of uniform thick-
ness throughout, the stock must usually be first roughly shaped
to fill the die impressions. The die recess known as the fuller is
of such form that when the stock is forged in it the stock will fill
the roughing and finishing impressions when struck. The stock
is drawn out in this recess in the same manner as the blacksmith
FORGING DIES §54
draws out stock under the trip hammer. When the fuller is
of such shape that the stock may be rolled in it, it is frequently-
called a roller. Again, when a die has a fuller but no break-
down, the fuller is some-
times spoken of as a break-
down. Fullers are very
frequently required in drop-
forging dies. In Fig. 4 a
forging is shown that is
made in the dies shown in
Fig. 5. In Fig. 5 (a) is
shown the top die, in (b) the bottom die, and at a the fuller.
In Fig. 6 (a), the forging is shown as it leaves the fuller.
After being shaped in the fuller, it is often necessary to dis-
tribute the metal by bending and otherwise shaping it in a side
Fig. 5
impression called the breakdown, edger, bending impres-sion, or side cut. As a rule, the breakdown is so located
that when the work is in it the work stands at right angles to
§54 FORGING DIES
the position it occupies when in the finishing impression. Thebreakdown is located on the right-hand side of the die, as it
is easier for the operator to swing the bar on that side. In
Fig. 5 the breakdown is shown at b, and in Fig. 6 (6) the forging
is shown as it leaves the breakdown.
5. After being shaped in the breakdown, the forging is
formed nearly to its finished dimensions in the roughing impres-
sion c, Fig. 5, and then finished in the finishiag impression d.
In Fig. 6 (c) the work is shown as it leaves the finishing impres-
sion. In some cases the roughing impression is omitted and the
forging is both roughed
and finished in the one
impression. It is muchbetter however, except
in those cases where
there is very little forg-
ing to be done, to use
the two impressions, as
the dies will last muchlonger, the severe duty
of completely forming
the forging being saved
from the finishing im-
pression. In the case
of large forgings the
finishing impression is
made on a separate set
of die blocks, and the dies are secured to another hammerlocated so that either hammer can conveniently be used. In
the case of small forgings made in large numbers, two finishing
impressions are often made in the dies. When this is donethe dies last longer, for after one of the finishing dies wears
out another is available.
6. Drop-Haininer Die Fastenings.—The manner of
fastening drop-hammer dies depends somewhat on the character
of the work being done. For heavy forging operations the
dies are usually fastened with two keys, one on each side of
6 FORGING DIES § 54
a dovetail or feather on the back of the die. Sometimes two
sHghtly tapered keys having straight sides are driven from
opposite directions, but on the same side of the die, so as to
clamp the die with an even parallel bearing on both sides. For
light work, with forming dies operating on thin metal, either
hot or cold, the lower die is usually held by means of poppets
with adjusting screws. The use of these poppets permits
considerable adjustment of the die; but they would not be
strong enough to hold the dies in place for heavy forging. Apocket is sometimes formed in the anvil face, so that a suitable
projection on the die may fit into this pocket and thus aid in
keeping it in its proper position.
7. Fin Formed on Forgings.—If the work being forged
is of circular cross-section, and so formed in relation to its axis
that the piece can be revolved, as, for instance, the handle
Fig. 7
shown in Fig. 7 (a), the forging dies will be made as shown by
the cross-section in Fig. 7 (5). The form in both dies corre-
sponds to the form to be given to the work, but the comers a
are rounded, so as not to scar the work. By rotating the work
as it is being forged, it will finally be brought to thie desired
circular cross-section, as indicated by the dotted circle at b,
and there need be no burr on the finished forging.
8. In the case of work that is not round in cross-section, or
which does not have a straight axis, it is impossible to turn
the piece in the die, and, hence, it must be forged to shape
without rotation. Dies are made that can be used for a series
of impressions or operations, some parts of the dies acting on
the edges, and others on the faces of the work. The finishing
die always squeezes out some metal on the edge of the work,
as shown in Fig. 8 (a). This metal formed on drop-forged work
is known as the fin, and provision is usually made for it by a
54 FORGING DIES
groove in the die, known as the flash, as shown at a, Fig. 8 (b).
The fin is also sometimes called the flash. On the average-size
dies, the flash is a flat shallow recess about ^ inch deep and
f inch wide. On larger dies the flash is deeper and wider.
The upper die is usually made with a back flash, or gutter,
as shown at b, in addition to the flash. This back flash is
generally milled about j inch from the impression and about
^ inch deep. It receives the excess metal after it is squeezed
through the flash. No flash is milled in the roughing impression,
as the metal does not quite fill
the recess when struck. Thefinishing impression only is
provided with flash and back
flash. In Fig. 8 (a) , c is the fin
formed by the flash, and d the
fin formed by the back flash.
9. Gate and Sprue.Drop forgings are usually
made complete while still a
part of the original bar. Thebar is thinned down where it
connects with the forging, and
the channel in the die that
forms this connection is knownas the gate. The gate extends
from the edge of the die block
to the front end of the impres-
sion. Each impression must have a gate. The size of the
gate should be such that it will support the forging while being
worked. The gate is enlarged at the edge of the die block to
form an opening called the sprue, shown in Fig. 5 at e. This
sprue is large enough to admit the rough bar. In Fig. 5 the gate
is omitted owing to the fact that the forging is small. In this case,
the flash extends to the sprue and serves the purpose of the gate.
10. Severing Work From Bar.—The fin is removed from
the forging in a separate operation. If removed while hot, the
operation is known as hot trimming. If the forgings are
207—5
FORGING DIES §54
hot trimmed, they are cut clean from the bar on the trimming
press, and the fin that remains attached to the bar is removed
by a cut-off attached to the bolster plates of the trimming press.
In this case, the forging dies do not require a cut-off. If the
fin is not removed till cold, the operation is known as cold
trimming. Most small forgings are cold trimmed. Whencold trimmed, the forgings are severed from the bar when hot
by the use of a cut-off forming part of the forging dies. The
cut-off is generally placed across, or dovetailed to, one of the
two rear comers, wherever there is the most room, as shown in
Fig. 5, at /. It is made by forming a chisel-shaped part on
each die. The edges of the cut-off are not, however, made sharp,
but are made with a face g about | inch wide so that they
will last long in use. In
some cases, as when dove-
tailed into the die block, the
cut-off is made of separate
pieces set into the dies so
that they may be readily
replaced in case they are
broken.
Fig. 911. Removal of Fin.
In Fig. 9, the cold-trimming
die and punch used to trim the fin from the forging shown in
Fig. 4 are shown. The die consists of the two parts a and b,
and c is the pimch. The die is in two parts owing to the fact
that it may then be more readily made, and it also provides a
means of adjustment for wear. It is secured to the bed of
the press by means of keys, bolts, or clamps. The punch c is
secured to the ram of the press. In operation, the forging, with
the fin attached, is placed over the opening in the die, after
which the punch is caused to descend and force the finished
forging through the die. The forging drops through the base
of the machine. The fin remains on the top of the die or
sticks to the punch and rises with it. Generally, strippers are
arranged to remove the fin from the punch as it ascends.
The fin is then brushed aside and the operation is continued.
54 FORGING DIES
When the forgings are hot trimmed, the trimming die andcut-off are generally both attached to the bolster plate of the
press. In Fig. 10, one form of bolster plate is shown. It is
Fig. 10
secured to the bed of the press by means of the holes a, and
the trimming die is set in the recess h and held in place by the
screws c. The cut-off tool d is next attached to the part e bymeans of screws that fit in the holes /, and the cut-off tool g is
attached to the ram of the press. In operation, the forging is
punched clean from the fin while hot, and the fin is then severed
from the bar by means of the cut-off. The hot-trimming press
should usually be located close to the hammer and furnace;
for, as a rule, the forging is trimmed, without reheating, as
soon as it is taken from the hammer.
EXAMPLES OF DROP-FORGING DIES
12. Dies for Open-Eiid Wrench.—The process of drop
forging is illustrated by the making of an ordinary open-end
wrench, shown in Fig. 11. A bar of suitable size to form the
piece is selected and a portion of
it may be formed under a power
hammer, or between suitable drop-
forging dies, so as to leave sufficient
material for the head, while the handle is narrowed some-
what. The dies for doing the work are shown in Fig. 12. Thepiece is first placed in the die opening a, which will form it
Fig. 11
10 FORGING DIES §54
as shown at /, the end of the die acting as a fuller to spread
the stock for the head. The work in all cases is held by the
sprue k. After the piece has been struck one or two blows
Fig. 12
in the opening a, it is placed in the opening h, and struck
several successive blows. This brings the entire wrench to the
finished form, except for the fia shown at h in the piece at the
§54 FORGING DIES 11
right of the dies, the wrench being shown at g. The piece is
now placed in the trimming die c and struck by the punch d.
This drives the wrench into the space s, from which it is removed
Fig. 13
endwise, in the form shown at r, and leaving the fin on the top
of the die block. The sprue k is then cut off, which completes
the forging. Instead of forming a portion of the stock under a
power hammer, or between separate dies, a fuller similar to
the one shown in Fig. 5 at a may be made a part of the dies and
used to shape the stock. The trimming die c, Fig. 12, is built
up of four pieces that are screwed together as shown. This is
done because the die can then be more easily made, and also
because, when one part becomes broken or worn out, it may be
replaced without making an entire new die.
Fig. 14
13. Dies for Single-Throw Crank-Shaft.—An inter-
esting example in drop forging is the making of the single-
throw crank-shaft shown in Fig. 13. In Fig. 14, the dies for
12 FORGING DIES 54
breaking down the stock and forming the disks a, Fig. 13,
pin b, and adjacent parts of the forging are shown. Theremainder of the ends of the shaft are forged under an ordinary
trip hammer. By the use of the short dies shown, a small
amount of stock is acted on and the forging can be made under
a Hghter hammer than would otherwise be required. Theforging is made from square stock, by passing it back and
forth from the breakdown c, Fig. 14, to the roughing impression d,
a tong hold having first been forged on its end. All the corners
of the roughing impression are weU rounded to prevent cold
Fig. 15
shuts. In the figure, e is the top die and / the bottom die.
The part g of the top die is made separately and dovetailed
into the side of the block.
14. After the stock is distributed in the roughing impression,
it is placed in the finishing dies shown in Fig. 15 and forged to
size by a few blows of the hammer. In the figure, h is the top
die and i the bottom die. The flash is shown at / and the back
flash at k. The impression in the finishing die is like that of
the roughing impression, except that the comers are not rounded
so much. Two hammers are necessary for this job, one for the
54 FORGING DIES 13
roughing dies and one for the finishing dies. These should
be located near each other and near to the furnace, so that no
time will be lost in going from one to the other. The trimming
Fig. 16
punch is shown in Fig. 16 (a), and the trimming die in (6).
The die is made in two parts I and m and is left open at the
front end n for hot trimming. The punch is milled out as
shown at o to receive the forging so that it will not bend during
the trimming operation. As the trimming is done hot, and
generally without reheating after forging, the press should be
located near the hammer on which the finishing is done. After
the trimming is done, the crank-shaft is finished by drawing out
the ends of the stock under a trip hammer.
Fig. 17
15. Dies for Four-Throw Crank-Shaft.—The forging
of the four-throw crank-shaft shown in Fig. 17, unlike that of
the single-throrr shaft just explained, can be most readily
Fig. 18
14
§54 FORGING DIES 15
completed m the dies; for in this case nothing would be gained
by forging the ends under a trip hammer. In Fig. 18, the dies
for breaking down and roughly forming the shaft are shown,
the top die being shown in (a) and the bottom die in (6). Thestock from which the shaft is forged, which is a little larger in
diameter than the bearings, is shown in Fig. 19 (a). In Fig. 18,
the breakdown is shown at a and the roughing impression at h.
The roughing impression is shaped like the shaft except that
the comers are slightly rounded to prevent cold shuts. In
Fig. 19 (6), the stock is shown after being forged in the break-
down, and in (c) it is shown as it leaves the finishing impression.
The finishing is done by a few blows of the hammer after
Fig. 20
locating the work properly in the finishing dies shown in Fig. 20,
the die shown in (a) being the bottom die and that in (6) the
top die. In the figure, the flash is shown at c and the back
flash at d. The comers are not rounded as much as those of
the roughing impression. As explained before, no flash or
back flash is provided on the roughing impression.
16. Two hammers are required to forge this shaft, one for
the roughing dies and one for the finishing dies. Both of these
should be located within easy reach of the heating furnace, for
convenience in operating. In case only a few of the shafts are
16 FORGING DIES §54
to be made, or where less accurate work would be satisfactory,
the finishing dies may be omitted and ti^e roughing and finishing
may be done in the same impression. In that case, only one
hammer is required to forge the shaft, and the cost of forging
is materially reduced. The fin e, Fig. 19 (c), is removed by the
Fig. 21
use of the trimming die and punch shown in Fig. 21 (a) and (b),
respectively. The trimming is done hot. The die is made in
two parts / and g, for convenience, and these parts are attached
to the bed of the press by means of bolts that pass through
the holes h. The punch is milled out as shown at i to receive
the forging and to guide the shaft while pushing it through the
trimmirjg die. As the shaft is trimmed hot immediately after
the forging is finished, the trimming press should be located
reasonably near the hammer on which the forging is completed.
The shaft as it leaves the trimming press is shown in Fig. 19 (d).
After trimming, the shafts may be straightened on a hydraulic
press, or in some other convenient way, and then remo^^ed to
the machine shop, where they are finished to size.
17. Dies for Flanged Piece.—Suppose the forging, twoviews of which are shown in Fig. 22, is to be drop forged. This
may be done by the use of the set of dies shown in Fig. 23;
in (a) the bottom die is shown and in (b) the top die. This
Fig. 22
Fig. 23
17
18 FORGING DIES 54
forging is made of round bar stock, which is first rolled in the
fuller a, after which it is broken down in the breakdown b.
The stock is then formed nearly to shape in the roughing
impression c, after which it is finished in the impression d by
a few blows of the hammer. The sprues and gates for the
various impressions are shown at e and /, respectively. The
stock as it leaves the fuller is shown in Fig. 24 (a) ; in (6) it is
shown as it leaves the breakdown; and in (c) as it leaves the
finishing impression. The fin g, shown in (c), is removed by
hoc trimming, using the trimming die shown in Fig. 25 (a) and
the trimming punch shown in (b). The die is made in two
parts h and i, which are doweled together by the pin ; of the
part h, which fits into a dowel hole in the part i. The die parts
are clamped to the bolster plate of the press. The part k of
the punch is made to fit into the ram of the press. After the
work is trimmed, the fin is cut ofif the bar by the use of the cut-
off, or side shear, attached to the press as previously explained,
54 FORGING DIES 19
Fig. 25
and the end of the remainder of the bar is again placed in the
furnace. Another forging is then made from the bar. Usually
several bars are^
heated at the same ll'lll'li'll''' fc^ ^
time so that another
bar will always be at
the proper heat for
forging as soon as one
forging is finished.
18. Two- Oper-ation Dies.—It is
not always possible
to make one set of
forging dies produce the work, and in other cases the work
cannot readily be shaped with a single set. In both of these
cases, it is generally possible to do the work by first making
a preliminary forging, in one set of dies, and then finishing
the forging in another set. When this is done, the work is
spoken of as a two-operation job, and the dies used as two-
operation dies. The forging of the steering knuckle shown in
Fig. 26 is an example of work that
can be most readily forged in two-
operation dies. In Fig. 27, the dies
in which the work is first forged are
shown, the bottom die being shownin (a) and the top die in (b). Thebreakdown is shown at a, the form-
ing impression at b, and the work
as it leaves the dies is shown in
Fig. 28 (a). A view of the cross-sec-
tion at ab is shown in (b) . Theforging is next trimmed while hot,
using the trimming die shown in
Fig. 29 (a), and the trimming punchshown in (b), after which it appears as shown in Fig. 30 (a).
This completes the first operation, which is in fact the makingof a complete forging, though not the one finally desired.
Fig. 26
'Jp
M
UM
M
M
22
24 FORGING DIES 54
The arms c and d, Fig. 30 (a), are next straightened out by
the use of a hammer tiU the work appears as shown in (6),
after which the work is forged to its finished dimensions in the
JFig. 34
dies shown in Fig. 31. In the figure, the bottom die is shown
in (a) and the top die in (6). The forging now appears as
shown in Fig. 32. The fin e is then removed by hot trimming,
using the trimming die showm in Fig. 33 (a), and the trim-
ming punch shown in (6). This completes the second operation,
and the forging appears as shown in Fig. 26.
19. Dies for Long SpaimerWrench.—The dropforgingof
the long spannerwrench
shown in Fig. 34 is an-
other example of a two-
operation job, although
in this case the forging
is finished in one pair
of dies. This forging is
made in two operations
in order to reduce the
size of the dies required
to forge it, and to en-
able the work to be
done on a much smaller
hammer. The wrench
is made by forging the
large end first and it is
then reversed and the
other end is forged.
The upper die is shown in Fig. 35 (a) and the lower die in {h)
.
The breakdown is shown at a, which breaks down the stock that
forms the large end of the wrench, no breakdown being required
for the small end. At h is shown the forming impression for the
Fig. 35
54 FORGING DIES 25
large end of the wrench, and at c the forming impression for the
small end. The notches d and e serve as locating points and to
prevent the metal from sliding forwards when struck. When
the large end of the wrencn is forged, lugs are formed on it by
the notches d. These lugs fit into the notches e of the impres-
sion c, and thus locate the work in the forming impression for
the small end. The part/ in (a), known as the horn, or bender,
is a separate piece that is dovetailed
in place. The large end of the forg-
ing is trimmed by the use of the die a,
shown in Fig. 36 (a) , and the punch h;
and the small end is trimmed by the
use of the die c, shown in {h), andthe punch d, the forging being hot
trimmed. The small end is then
moved backwards in the trimming die far enough so that the lugs
formed on the sides may be removed with another stroke of the
press. After trimming off these lugs, the wrench is struck again in
the forging dies to round the edges where the lugs were sheared off.
Fig. 37
26 FORGING DIES §54
20, Dies for Axle Clip.—The making of the axle clip
shown in Fig. 37 (a) involves the following operations: Forging
and welding, hot trimming, hot bending, threading, cold bend-
ing, and punching. The part shown in (b) forms the lugs a of
§54 FORGING DIES 27
the clip, shown in (a). These pario are made first by the use
of a set of dies not shown. They are then welded to the stock
forming the rest of the clip, after which they are drop forged.
The welding and forging are done in the dies shown in Fig. 38 (a)
and (b), the bottom die being shown in (a) and the upper die
in (6) . To make the weld, a part like that shown in Fig. 37 (6)
is placed at b, Fig. 38 (a), the stock for the main part is laid
on it, and the upper die is dropped, sticking the parts together.
The work is now reheated, another piece like that shown in
Fig. 37 (b) is put on the lower die at b, the heated part is then
placed in the die with the part previously stuck to the bar in
the recess c, and the upper die is again dropped, sticking the
two parts together and
at the same time forging
and welding the clip . Theworknow appears asshown
in (c), d being the forg-
ing, e the fin, and / the
part stuck to the bar to
become part of the next
forging. The fin is next
trimmed off while the workis still hot. The trimming
die is shown in (d) and the
punch in (e) . When trim-
ming, the work is supported on the die by the fin, and the punch,
descending, forces the forging through the die. In Fig. 39 (a) the
forging is shown as it now appears, and at b in (6) the fin is
shown removed from the work. The cut-off g in Fig. 38 (e) also
severs the fin b in Fig. 39 (6) from the stock c, as shown at d.
Fig. 39
21. After trimming, the forging is still hot. It is nowpicked up with a pair of tongs and placed on the bending die
shown in Fig. 40 (a), secured to the bolster of an adjacent
press, after which it is bent to the shape shown in (b) on the
downward stroke of the punch, which is illustrated in (c).
The forging is located on the die by the locating gauges g shown
in (a), in which the lugs a, Fig. 39 (a), fit. The recesses i,
28 FORGING DIES 54
Fig. 40 (c), on the side of the punch, receive the lugs when bent,
and the recess ; receives the end k of the forging, shown in {b).
After the forging has cooled, the ends k and / are threaded, and
then bent to the form shown in Fig. 37 (a) by the die shown
in Fig. 40 {d) and the punch shown in {e). To bend the forg-
ings, each piece is in turn placed in the die, with the ends k
and /, shown in {h), in the grooves m and n of {d), the lugs o,
in (6) , occupying the recess p in id) . The punch then descends
Fig. 40
and bends the forging to the desired shape, the end h, Fig. 37 (a),
occupying the recess r, Fig. 40 {e). After the bending is com-
pleted, the holes c, Fig. 37 (a), are punched in the work, using
the die and die holder shown in Fig. 40 (/), and the punchshown in (g). In (/), t is the die, u the gauge and stripper
plate, and v the holder. The die t is shown removed in {h).
To locate the work for punching, one of the lugs a, Fig. 37 (a),
§54 FORGING DIES 29
is placed in the opening w, Fig. 40 (/), while the other is placed
in the opening x and against a stop between the die t and
stripper u. The punch on descending forces the punching downinto the opening w. The work is then withdrawn and the other
lug inserted in the opening x and punched.
The equipment needed to forge this piece is a furnace and
hammer to make the part shown in Fig. 37 (b), and a furnace,
hammer, press for trimming, and press for bending, conveniently
arranged to bring the work to the form shown in Fig. 40 (6).
A threading machine, press for bending, and press for punching
are used to finish the work when cold.
HEADING AN© BENDING DIES
HEADING-MACHINE DIES
22. Principle of the Heading Machine.—Headingmachines are used principally to upset hot metal. To do this,
the work is first gripped in a set of dies a, b, Fig. 41, that are
recessed to the form of the
forging desired. The machineis so constructed that one of
the dies may be moved in
the direction of one of the
arrows c or J by operating a
foot treadle; and when the
dies are closed on the work,
which is placed in the recess e,
the work is held between them while the heading tool, or
plunger, / moves forward in the direction of the arrow g and
forces the hot metal into the recess in the dies. The plunger
then moves backwards, the dies open, and the work is removed,
after which the operation is repeated. As the forgings are
usually made from bar stock, some provision must be made so
that just enough stock will extend out in front of the dies to fill
the recess when struck by the plunger. This length is generally
determined by trial, and then a gauge, or back stop, h is set to
Fig. 41
30 FORGING DIES §54
the proper distance ahead of the dies. The bar is then placed
against this gauge and is thus correctly located. The gauge is
so controlled by the mechanism of the machine that it moves out
of the way as the plunger moves forwards, and then automatically
returns after the plunger moves back again. Ordinarily, one,
two, or three grooves are made in the dies and one, two, or three
heading tools are fitted into the machine at a time. In this
way, two or three upsetting operations can be performed on a
piece of work without changing the dies.
23. Heading Dies for Hexagon-Headed Bolt.—Suppose
the hexagon-headed bolt shown in Fig. 42 (a) is to be forged
in a heading machine. This can readily be done by the use of
(b) (c) (e)
Fig. 42
the dies shown in (b) and (c) and the heading tool shown in (d).
The stock is first located in the lower groove a, by the use of
a gauge, not shown, after which it is upset by a blow with the
heading tool b. It then appears as shown in (e). The next
step is to place the head in the groove c, no gauge being required
to locate the bolt at this setting, as the head already formed fits
into' the recess in the die. The work is finished by a blow with
the heading tool d.
The heading tools b and d are held in place in the tool holder g
by the setscrews h and i. In case the head need not be so
well finished, the second operation will not be required and the
head may be formed by the use of the lower groove a and the
tool b only. The dies a and c are each made in two parts, and
54 FORGING DIES 31
are keyed together by the keys / and k. The bottom grooves I
and m fit keys that are set in the machine, and by their use the
dies are properly located relative to each other.
24. Dies for Bent Handles.—^Work of the form shown
in Fig. 43 (a) may be forged on a heading machine, the work
being shaped by the set of dies shown in (6) and (c) . The dies
are shown in perspective in Fig. 44. In these illustrations the
32 FORGING DIES 54
the die. The stock is next reheated, and gripped in the depi'es-
sion d in the lower die, after which the plunger forces the metal
into the opening e. The work is now placed in the depression /and a punch secured to the plunger punches the hole g, in
the upset portion, and the punching passes out through h.
Fig. 44
Without reheating, the work is placed in the groove i on the
top die, and the dies are again closed, the bending tool j forming
the right-angled bend k.
BENDING DIES
25. Use of Bending Dies.—When it is necessary to
bend heavy hot metal to various shapes, a form of horizontal
press, known as the bulldozer, to which a set of bending dies
has been attached, is used. In Fig. 45, one form of bulldozer
is shown, the bending dies a and b, being shown set up. Theconnecting-rods c, which are driven by a system of gears and
pulleys, drive the ram d to which the movable die b is secured.
During the operation, the die a remains stationary, while the
movable die b advances and bends the metal to the shape of
the dies. The dies shown are made to form the piece of work
shown at /. To bend the work, a straight bar of hot metal,
§54 FORGING DIES 33
that has been cut to the required length, is laid on edge against
the face of the stationary die a, the machine is then started,
and the movable die b advances slowly, and bends the stock to
the outline of the
dies. The dies are
almost always madeof cast iron, and are
usually made ribbed,
instead of solid, in
order to lighten them.
As a rule, drawings of
the dies are made in
the drafting room,
after which the dies
are cast, and then
planed to the required
dimensions in the machine shop. For a large variety of work,
however, no machining is necessary, as satisfactory work maybe turned out by using the dies just as they come from the
foundry. Dies of this class are used to bend a very large variety
of work, as forgings for car trucks, agricultural implements, etc.
Fig. 45
26. Simple Bending Dies.—A simple form of bending
die is shown in Fig. 46. Here the stationary die is shown at a
and the movable die at c. They are so formed that when the
movable die is forced
against the blankstrip of stock b, indi-
cated by dotted lines,
it will be bent to the
required shape. In a
bending die, someform of gauge or
stop may be used in
order to locate the
blank properly; this must be made to suit the shape of
the blank, and in its simplest form may be a shoulder, as
shown at d.
Fig. 46
34 FORGING DIES 54
Fig. 47
27. Cold Bending.—When the piece that has been bent
cold, as, for instance, that shown in Fig. 47, is examined, it
will be found to have a shape slightly different from that of
the die. Thus, if the dotted lines represent the shape of the
piece while between the faces of the dies, on removal it will
assume the shape shown in full lines,
by reason of the elasticity of the ma-terial. Hence, it follows that for elastic
materials the bending surfaces must be
arranged to bend slightly beyond the
required angle; how much beyond must be determined byexperiment in each particular case. In general, the amount will
be least for compar-
atively non-elastic
materials, as an-
nealed iron, copper,
or brass, and most
for more perfectly
elastic metals, as
spring steel, hard
brass, etc. Withmetals like lead, or
hot metals, no al-
lowance need be
made.
28. Wing Dies.
Fig. 48 shows a
form of wing die
that has hingedparts, or wings, w,
and is well adapted
for use in a bull-
dozer. As the punch c advances, the wings w of the die a are
folded in by the die d, thus bending the iron b without stretching
it. The part d acts as a cam to close the wings of the die.
The illustration shows a piece of stock b, with the wings wclosed about it ; the dotted lines at w' show the position of the
Fig. 48
§54 FORGING DIES 35
wings when the die is open. When the wings are open,
the flat piece of stock is laid against them. When working
cold metal, if the punch c is made with parallel sides, as in the
figure, the work will not come out parallel, as at h and h' , but
will be somewhat divergent, as at e, on account of the elasticity
of the metal. To overcome this, the punch must be made with
its edges a little convergent, so that the work when closed will
have somewhat the appearance of the piece shown at f. Thesubsequent expanding when released will restore it to a parallel
form. The amount of this divergence depends on the kind of
metal and the amount that it is heated. If entirely red hot
when finished, it will act something like lead, which is prac-
tically non-elastic. As the metal is partly cooled when com-
pressed between the cold or nearly cold dies, it may not have
the exact form of the die when cold.
CONSTRUCTION OF FORGING DIES
MATERIALS AND EQUIPMENT
29. Materials.—In places where only a few forgings are
produced, the dies are frequently made from a close-grained
cast iron, the faces being cast to approximately the correct
form and finished with a file or a scraper. Large forming
dies have been cast so perfect that practically no finish was
required. Cast-iron dies are sometimes made with chilled
faces, to increase their hardness and wearing qualities. Ordi-
nary dies for making large quantities of duplicate work are
made from steel, both steel castings and well-annealed steel
forgings being very largely used. In most cases these are cast
or forged smooth on the face, and the desired forms are cut in
them by milling, chipping, and scraping.
30. In cases where a very large amount of work is to be
done, the dies may be made of about .60-carbon open-hearth
steel, and one or both of the dies are then hardened by heating
them to a cherry red heat and immersing them in a bath of
36 FORGING DIES § 54
water or brine. T'hese dies must afterwards be tempered to
make them less brittle and relieve the internal stresses. Dies
for large forgings are often made of about .80-carbon steel,
and left unhardened. This is done to reduce the danger of
checking or cracking in hardening, the unhardened steel being
hard enough to resist the tendency to stretch. Again, dies that
have thin projections in the recesses are frequently made of
about .80-carbon steel and not hardened; for if the die were
hardened, the thin projections would likely break off. In case
the dies are to be used to forge tool steel or other hard steel, a
steel fairly high in carbon is generally used. When the material
of the dies is too low in carbon, the force of the hammer blows
it receives in service may cause the central part of the die face
to sink below the level of the rest of the die. This is known as
disliiiig. Dishing may be prevented by using a tool steel for
the dies, and then hardening the dies to a sufificient depth to
withstand the tendency to dish.
31. Die-Siilking: Machine.—^As die making is a branch
of toolmaking, the equipment used for the one is, as might be
expected, largely the same for the other. The machines most
commonly used for die making are lathes, shapers, milling
machines, drill presses, and die-sinking machines. In Fig. 49
one form of machine especially adapted to die sinking is shown.
The machine is a form of vertical milling machine in which the
work is held in the vise a that is attached to the table b. This
table may be moved crosswise by means of the hand wheel c,
and lengthwise by means of the hand wheel d or by operating
the longitudinal power feed by means of the lever e. Thecutting tool, which of course revolves, is held in one of the
spindles / and g. The head h of the machine is moved up and
down by means of the hand wheel i, and the spindles are driven
by belt and gearing operating through the pulleys / and k,
and the shaft I. The weight of the head h is balanced by
means of weights that are attached to the chain m. The die
block to be machined is secured in the vise a.
32. As a single spindle large enough to withstand heavy
cuts cannot be provided with a sufficient range of speed to
§54 FORGING DIES 37
suit the delicate cuts made with small cutters and the low speeds
required for the large heavy cuts, two spindles / and g are
Fig. 49
provided, / being the larger and used for the heavy cutting.
Either spindle may be used, as desired. A quick hand return
38 FORGING DIES §54
for the table is obtained by using the crank n, which fits the
square on the end of the screw, and adjusting the lock bolt o.
The feed is driven through the pulleys p, q, and r and the belts 5
and t. The pulley / is the main driving pulley, and is driven,
in turn, by a countershaft connection or an electric motor, as
found most convenient. The table stops u may be set as
desired. As they pass the lever v, they automatically throw oflf
the feed. The cutters used on the machine may have either
tapered or straight shanks. Those having tapered shanks
may fit directly in the spindles, or they may fit a socket that
fits the spindle holes ; and those having straight shanks are used
in a chuck made for the purpose as, for example, the one shown
Fig. 50
in Fig. 50. The shank a of this chuck fits the spindle of the
machine; the split bushings, b, c, and d, fit in the nut e, and the
nut is then screwed onto the shank, clamping the bushings on
the cutters. Bushings, / and g, of smaller size, may be made to
fit into the larger bushings, in order to accomodate smaller
tools.
33. Instead of the vise a, Fig. 49, a form of rotary vise,
as the one shown in Fig. 51, may often be used to advantage
on a die-sinking machine. By its use, short arcs may be cut
much quicker than in any other way. To use this attachment,
the table a of the machine and the vise b are set, by lining up
the indicating marks placed upon them for the purpose, sO'
that the center about which the vise rotates when in use will
§54 FORGING DIES 39
be directly in line with the spindle of the machine. Theindicating marks are not shown in the illustration. When the
marks are once established, the machine may be readily set
up for circular milling at any future time. After setting up the
vise and table, a pointed center is placed in the chuck and the
chuck is put in the spindle. The die block is next located and
clamped in the vise so that the center point of the arc to be
m.illed is directly under the pointed center in the chuck. The
table may then be moved off center far enough so that the
cutter will mill the impression desired when the vise is rotated
by means of the hand wheel shown at c. The pointed center
is now removed from the chuck, a cutter of the desired form
is put in it, and the impression is milled to the desired depth.
Fig. 51
34, Die-Sinking Tools and Cherries.—In Fig. 52 are
shown a few of the large variety of cutters and long slender
milling tools, called cherries, used in die making. Those
shown at a, b, c, and d are made with tapered shanks to fit the
tapered holes in the spindles of the machines, while the rest of
the cutters shown are made with straight shanks and are held
in a chuck similar to the one shown in Fig. 50. The tool
shown at e, Fig. 52, is an ordinary pointed center that is made
Fig. 52
u V
40
§ 54 FORGING DIES 41
to fit a chuck. It is used when it is desired to line up the
spindle of the die-sinking machine with a point on the die
block, as, for example, when setting up work in the circular
vise. The tool shown at a is a roughing cutter, and, as its
name implies, is used only to quickly remove large amountsof metal without regard to a fine finish. A 5° cutter is shownat b, a 7° cutter at /, a 10° cutter at g, and a trimming cutter
at c. The 5°, 7°, and 10° cutters are used to finish the sides of
the impressions, and when so used, a taper, or draft, of 5°, 7°,
or 10° is provided, so that the forging can be easily removedfrom the dies. A large variety of special forming cutters are
used in die sinking, a few of these being shown at d, h, i, j, k,
and I. At m, a 45° cutter is shown, while the ones shown at nand o are special cutters. At p, q, r, s, t, u, and v, a few of the
large number of different shapes of cherries are shown, these
being of the average type. Cherries are made of almost anyform to suit the impression to be made in the die block.
35. Cherrying Attachment.—A cherry is a milling
cutter usually made together with its arbor as one piece, the
length of the arbor varying with the requirements of the workto be done. Cherries are used, as a rule, on some form of
universal milling machine or, in an attachment for the purpose,
on a die-sinking machine. When one-half of an impression is
cylindrical, cherries are used to mill out the stock, the shank
of the cherry being made the same diameter as that of the
sprue. The cherry is then sunk into the work until the shank
comes in contact with the sprue. This operation is known as
cherrying. In Fig. 53, a cherrying attachment a for the die-
sinking machine is shown attached to the large spindle b of the
die-sinking machine. It is clamped to the under side of the
head c, and may be swiveled and securely clamped in different
positions. The tapered hole d is the same as that of the spindle
of the machine and, consequently, the same arbors that fit in
the one may be used in the other. The purpose of the attach-
ment is to bring the axis of the cutting tool horizontal instead
of vertical, as this is the most convenient arrangement for
cherrying.
42 FORGING DIES §54
36. Ball Vise, Hammer, and Templet Holder.—Therecesses in the die blocks are usually finished by hand work, such
as chipping, scraping, riffling, typing, and polishing. To facili-
tate this work, the die blocks are usually held in a ball vise,
one form of which is shown in Fig. 54 (a). The die block is
clamped in the space a by the setscrew b, and the part c of the
vise rests on a pad of leather d which may be made by coiling
up a short length of 2-inch belt and riveting it together at
Fig. 53
intervals. By the use of this vise the work may be held at
any desired angle, the weight of the work being sufficient to
resist ordinary chipping.
The die maker generally uses a special hammer, shown in
Fig. 54 (6), for chipping. It is made with two flat faces.
As the outline of the recess to be sunk in a die block is usually
laid out on its face by the use of a templet, it is often found
convenient to use a holder of some form to hold the templet
firmly while scribing its outline on the block. One form of
54 FORGING DIES 43
templet holder is shown in Fig. 54 (c), in which / is the die
block on which the templet is clamped at g. To use this holder,
the legs h are first adjusted on the bar i to suit the work and
then clamped in place by the thimibscrews /. The templet
is then located on the
block, and the holder
is set in place, after
which the thumbscrews
k are tightened, and
the templet is then
forced firmly against
the face of the block
by adjusting the screws
/ and m. The screw mturns inside of /, this
arrangement being
used so that the screw
m may be easily forced
downwards without
turning it.
37. Chisels andScrapers.—Die mak-
er's chisels are gener-
ally forged from hexa-
gon or octagon tool
steel to the shapes best
suited to the work.
Some of the commonshapes are shown in
Fig. 55 (a) . The curved
and fiat shapes are used
mostly, although a large variety of irregular shapes are also
necessary. The flat chisels vary in width from ^ to | inch,
and the curved chisels are made with many different curves.
After most of the steel has been removed by milling andchipping, scrapers are used. The scrapers may be of the ordi-
nary three-cornered and half-round forms used by machinists
w ij
(")
§54 FORGING DIES 45
and toolmakers generally, but, ordinarily, they are made of
square and half-round stock in a variety of shapes, as shown
in Fig. 55 (b). They are short, they cut on the ends only,
and are made to fit in short round handles.
38. Rlfflers.—After the scraping is finished, rifflers, or
small bent files, are used to smooth the surface. In Fig. 56
a number of rifflers are shown. They are made in a large
variety of shapes, sizes, and cuts. The operation of removing
metal by the use of riifiers is known as riffling. The riffler is
held lightly in the hand and is worked back and forth over the
46 FORGING DIES §54
surface to be smoothed. Spoon rifflers, shown at a, are spoon
shaped and are made with many different curves. They are
the most commonly used of all rifflers, as by turning them
while riffling, different curved surfaces may be formed and
most spots in the recess can be reached. Flat rifflers b are
also largely used. They are made in many different shapes and
widths. At c and
d hook rifflers and
knife rifflers, and at
e half-round rifflers,
are shown.
39. Types.When the die re-
cesses are deep and
narrow, it is often
difficult or impossi-
ble to chip, scrape,
and riffle them to a
finish. When this
is the case, small
blocks of steel,
known as types,
whose ends are
shaped exactly like
that part of the
forging to beformed, are used.
These types are
turned, milled, and
filed to shape and
are then hardened
and drawn to a
purple color. A few forms of types are shown in Fig. 57. Theoperation of shaping a recess by the use of types is known as
typing. Where types are to be used, the recess is first milled
and chipped as near to the outline and depth as is safe, the type
is then rubbed lightly with Prussian blue, or some other marking
§ 51 FORGING DIES 47
material, then placed in the recess with a piece of copper or
some other soft metal on top of it, and struck hard into the
recess with a hammer. The marking material adheres to the
high places in the recess. These high places are next chipped
away and the operation of typing is repeated until the correct
shape is obtained, after which the impression is finished byriffling.
DIE-MAKING OPERATIONS
40. Choice of Style of Die.—As a rule, the die maker is
furnished with a drawing, a model of the finished part, or a
sample of the forgings that the dies are to make. Then the die
maker must know of what material the forging is to be madeand the finishing operations through which the forging is to
pass, in order that the correct allowances for shrinkage andfinishing may be made. The form of the dies is then deter-
mined. First, the die maker must decide whether both a rough-
ing and a finishing impression will be required and, if so, whether
the finishing impression should be made in a separate set of
die blocks. Other points then to be determined are whether
a fuller should be used, the direction the impression should
face in order that the best form of breakdown may be used, andthe hammer in which the dies are to be used, in order that the
dies may be made to fit that hammer. The die maker must also
decide whether the forging is to be trimmed hot or cold. Thedetermination of these points is largely a matter of judgmenton his part. This judgment is based on his previous experience
with dies made somewhat similar to the ones to be made, onthe experience of others, and on his own original ideas.
41. Planing' of Die Blocks.—The stock from which dies
are made is generally obtained from the rolling mills in bars
of the cross-sections desired, the bars usually being from 6 to
8 feet long. These bars are preferably prepared by planing
first the top surface and then down the left-hand side, about
2 inches, after which the bar is turned over and the bottom is
planed up forming a shank, or dovetail, of the proper bevel
and height to fit the machines in which the dies are to be used.
48 FORGING DIES § 54
From the bars thus prepared, blocks are then cut of any length
needed, after which the front side is planed to a depth of about
2 inches, care being taken to have this surface square with the
shank and the surface previously planed on the left-hand side
of the block. Instead of planing the entire length of the bar
at one setting, the bar may first be cut into the desired lengths
and each block planed separately. The first method is, how-
ever, to be preferred, as in this way the blocks can be prepared
much more cheaply. The object of planing the surfaces on
the front and left side of the die block is twofold; first, to pro-
vide working surfaces from which to lay out the die recesses,
and, second, to provide means to line up the dies in the hammer.
It should be noticed that the left-hand, and not the right-hand,
side of the die is planed. This is owing to the fact that the
breakdown is always located on the right-hand side, and,
consequently, this face would be destroyed when the breakdown
is formed.
42. Allowances for Shrinkage.—As all metals expand
when heated and contract when cooled, the recesses in the die
block must be made larger than the size of the forging when
cooled, to allow for this contraction or shrinkage. Shrinkage
is most conveniently allowed for by the use of a shrink rule.
When the forgings are to be cold trimmed, a shrinkage allow-
ance of 1^ inch to the foot is made, and when they are to be
hot trimmed, an allowance of | inch to the foot is made.
These allowances are the same, whether the forgings are to be
made of wrought iron, steel, copper, or bronze. The difference
in the allowances for hot and cold trimming is due to the fact
that, when hot trimmed, the forgings are generally struck a
finishing blow in the die after trimming, in order to straighten
them. As the forgings are relatively cold at this time, the
amount they will shrink will be less.
43. Allowances for Draft and Finish.—In case the
sides of the die recesses were made vertical, the forging would
stick in the die when struck. To prevent this, the sides of the
recesses are made to slant away from the vertical a little and
the allowance thus made is known as draft. The amount of
§54 FORGING DIES 49
draft varies from 3° to 10°. For a thin forging 3° is plenty, for
a deep die recess 7° is generally used, and for the central plug
in a recess a draft of 10° is used, as in this case the metal will
contract and grip the plug when cooling, and cause the forging
to stick if the draft is insufficient. When the surfaces are
curved or are at an angle with the vertical, no allowance is
made for draft. A draft of 3° corresponds to a taper of
Ye inch to the inch ; a draft of 5°, to a taper of -^ inch to the
inch ; a draft of 7°, to a taper of | inch to the inch ; and a draft
of 10°, to a taper of ys inch to the inch. The draft in the
recess is usually cut on the die-sinking machine, using a 3°, 5°,
7°, or 10° cutter.
In case some parts of the forging are to be machined after
forging, additional metal must be provided at those parts.
This allowance is known as the finish, allowance. It is
usually about -^ inch.
44. Laying- Out of Dies.—In Fig. 58 (a) is shown the
block for an upper die and in (b) that for a lower die. To lay
out the dies, the faces a and b are first covered with copper
sulphate, or blue vitrol, after which the center lines are scribed
on both, being located from the working faces c and d in one
case and e and/ in the other. The outline of the recesses should
be so located that the heaviest end of the forging will be at the
front of the dies, as the forging will then be easier to handle
while being worked and a good sized sprue may then be used.
In case the outline of the forging is simple and regular at the
joint line, the outline of the recesses may be laid out by the use
of a square and dividers; but a thin sheet-metal templet of the
forging is generally made for this purpose when the outline of
the forging is irregular. The same templet will do to lay out
both the lower and upper dies, and the trimming die and punch.
Two or three combination squares may be used to locate the
templet on the blocks in order that the outlines of the recesses
on both blocks will line perfectly. The templet g is first placed
in its proper position on one of the blocks, and is held there
by a templet holder while the outline is scribed on the block.
Combination squares h and i are then set from each of the
50 FORGING DIES 54
working faces of the block to the edge of the templet, after which
the templet holder is removed. The templet is then placed,
reversed, on the other block and located properly by the use of
the settings obtained on the combination squares, after which
it is clamped in place by the templet holder. The squares
are then removed, and the outline is scribed on the die block.
Fig. 58
The outlines on both blocks are then marked at intervals by
prick-punch marks so that they will not be destroyed. The
layout is completed by scribing lines for the flash, back flash,
gates, and sprues, and then prick-punching them as before.
§54 FORGING DIES 51
45. Machining: of Die Recesses.—The recesses in the
die blocks are shaped mainly by means of the die-sinking
machine, although other machines are frequently used. Parts
of the recesses may be formed by turning on a lathe. The
milling machine, drilling machine, planer, and shaper are also
quite often used.
46. The outlines scribed on the face of the block are used
as guides when cutting the recesses. After the outside of the
block has been finished and the parts that can be done on the
lathe have been turned, the die is set up on the die-sinking
machine, and the recesses are roughly cut to the lines laid out
on the face of the block. After the impressions are roughed
out nearly to size on the machines, they are finished by handwork. An example of a die block set up on a die-sinking
machine for the milling of a gate is illustrated in Fig. 59. Thedie block is shown at a, and at b is shown a cutter of the form
illustrated at /, Fig. 52, which is used for this operation. As a
rule, when milling the recesses, oil is needed only when special
forming cutters are used, and in that case lard oil is advisable.
At c, Fig. 59, is shown a brush that is kept available to brush
the chips out of the recess, and at d a. small tube is shown fitted
into a wooden holder e. This tube is used to blow the chips
out of the recesses. The electric lights shown at / may be
brought close to the work, when necessary.
The machine here shown differs from the one shown in Fig. 49,
in that the vertical movement is obtained by raising and lower-
ing the table of the machine instead of the cutter head. In
either case, the raising or lowering of the table is accomplished
by means of a hand wheel having a graduated dial that shows the
motion of the table or head in thousandths of an inch.
47. Other parts of the die may have to be machined bymeans of the cherrying attachment on the die-sinking machine,
or on the milling machine. The proper cherr}^ is placed in the
spindle of the machine, and the cherrying is done at this time.
When machining the recesses, care should be taken to leave as
little stock as possible to be removed by hand, as the handwork is much slower. For the last cut, the cutter should be
52 FORGING DIES § 54
brought as close as possible to the finished form of the die.
When the cutter is finally set for the last time, it should be
run over the work two or three times in order to get the smooth-
est surface possible. The final cut should just split the lines
scribed on the face of the die.
Fig. 59
48. Hand Finishing of Die Recesses.—After all the
machine work is done, the corners and irregular parts of the
recesses will still be unfinished. These are then chipped,
scraped, riffled, typed, and polished, the die being held in
the ball vise while doing the hand work. When chipping, it
is advisable to chip down or away from the outline of the
recess to avoid breaking out parts at the end of the cuts. Oil
should be used sparingly and light cuts should be taken. Care
§54 FORGING DIES 53
shotild be taken to try the templets and depth gauges often in
order not to take out too much stock.
By the use of the scraper, the high points left by the chipping
operation are reduced and the surface of the recess is madesmooth. The die is finished to its correct dimensions with the
scrapers, after which the surface is smoothed further by the
use of riffiers. The rifflers and scrapers must be worked over
the surface in different directions to prevent the formation of
grooves and ridges. In Fig. 60 is shown the operation of
scraping out a recess in the die block a, which is held in the ball
Fig. 60
vise b. The scrapers are shown at c. They are held in a rack
located conveniently so that any of them may be had at once
when needed.
A very smooth surface is required in the recesses of the die
so that the forging will have smooth surfaces and come from the
die easily. Every part must be carefully finished. This is
done by use of coarse emery cloth first, and then fine, wrapped
54 FORGING DIES § 54
around a file or a piece of wood. To polish the comers that
cannot be reached by the emery cloth, emery and oil are used
on the end of a small piece of wood, the emery embedding itself
in the wood.
49. Lettering of Die Recesses.—When lettering is
required on the forging, the dies are stamped in the bottom of
the recess with a deep fiat-faced letter that will give body to
the letters on the forging. If the letters are very large, the
recesses are chipped or milled out after lightly stamping the
letters in the die to locate them. They are then readily stamped
in the die to their full depth without removing much of the
steel. To locate the letters in the recess, the central letter, or
figure, is first stamped, and from this central letter the other
parts of the word, or figures, are added.
50. Lead Proofs of Die Recesses.—After the dies are
completed, a lead proof is usually made in order to check upthe dimensions and to see if there are any defective places in the
dies. To make the lead proof, the dies are cleaned, dusted
with powdered chalk, set on their ends with the die faces
together and with the working faces in line, and then securely
clamped with a large C clamp. The lead is then melted and
poured slowly and evenly into the dies. After the lead has
cooled, the dies are undamped and the lead is removed and
examined. If the lead shows any changes in the recesses to
be necessary they are then made, and another proof is made to
be sure that the dies are correct. As the shrinkage of lead is
about the same as that of steel, the finished forging will measure
nearly the same as the lead proof. In the case of forgings
made with holes in them, as, for example, any form of ring, the
shrinkage allowance will have to be made when checking up
the proof, owing to the fact that the hole in the forging is
formed by a plug in the die recess, and this plug prevents the
lead from shrinking when cooling. In the case of the forging,
however, the shrinkage will take place, since it is not in the
die while cooling. The finished forging will weigh about two-
thirds as much as the lead proof; thus the weight of metal
needed for the forging is readily determined.
§54 FORGING DIES 55'
51. Die Breakdowns.—The breakdown is not made in
the dies until the face recesses, the flashes, gates, and sprues
are finished. Then the dies are clamped together just as
they were to make the lead proof, and the rough surfaces of the
right-hand sides of the die blocks are chalked. The half of a
lead proof or a templet of the forging is now laid on the side of
the dies and the outline of the forging is scribed on them. If
this proof or templet is symmetrical as it lies on the side of the
dies, one-half of the outline should be located on each die; in
other respects, the position of the proof or templet is determined
by the experience of the die maker. The outline of the templet
is then scribed on the dies. Another line Ye iiich inside of this
line is scribed in all places. This is the working line of the
breakdown. The dimensions of the breakdown are madesmaller than those of the forging so that the broken-down stock
will readily lie in the forming impressions. All the corners of
the breakdown should be well rounded to avoid cold shuts
when forging, and all the vertical parts are given a draft of 7°.
The breakdown is made enough wider than the forging so that
there will be plenty of room for the work ; and it is made with a
gate and sprue. A cut-off is formed at its rear end to trim off
the extra stock drawn out under the fuller. After the correct
outline is determined, it is prick-punched to make it permanent,
and the die is then set up on the die-sinking machine, being set
on its side in the vise. Then, using a long straight cutter, the
breakdown recess is milled to the outline.
52. Hardening: and Tempering of Dies.—After the
breakdown is finished, the dies are ready to be hardened and
tempered. If the dies are made of steel containing less than
.60 carbon, it will be necessary to first carbonize their surfaces
by packing them in a box of granulated raw bone, or other
carbonizing material, and heating as explained in Hardening
and Tempering. Dies made of steel containing more than
.60 carbon need not be carbonized before hardening, and dies
made of steel containing over .80 carbon are generally not
hardened. To harden the dies, about 2 inches of burnt granu-
lated raw bone may be placed in cast-iron boxes having walls
207—8
56 FORGING DIES §54
about |-inch thick, cast iron being used because it stands the
heat well. The dies are then placed face down on the bone and
settled down so that the bone fills the recesses. Burnt bone is
used to prevent decarbonization of the steel and the formation of
scale. The box containing the dies is then placed in a furnace
and maintained at a temperature of from 1,425° F. to 1,450° F.
for from 6 to 8 hours, according to the size of the blocks.
53. When properly heated, the dies are quenched in a tank
in which the water supply discharges upwards, as shown in
Hardening and Tempering, and having two bars suspended across
its top to support the die. The water is turned on full force, as
soon as the die is properly placed, and strikes against the die
faces, thus preventing the formation of steam pockets. Wherethe dies are cold enough so that water will cling to their top
comers, they are placed in an oil quenching tank till cold.
The temper is drawn in oil, brought to a temperature of about
450° F. and kept at that temperature till the heat penetrates the
dies. After the dies are removed from the oil, the comers of the
recesses and the cut-off are drawn to about a purple color, using
a blow torch. When cold, the recesses are polished, using emery
and oil on the end of a stick, and the dies are then ready for use.
54. Trimming Dies.—The work of cold-trimming dies
is a great deal harder than that of hot-trimming dies and they
are usually made of high-carbon steel and hardened. Both the
die and punch are made in the same manner as the ordinary
blanking die and punch. A special grade of steel known as
hot-trimming die stock is used for dies intended to trim the
forgings while still hot. Ordinary tool steel is not suitable for
this purpose because the edges of a hardened die crack badly
after being in use a short time. The special grade of steel for
hot-trimming dies does not require hardening and the dies madeof it become tougher in use, and give very good service. Thehot-trimming dies are made in the same manner as are the cold-
trimming dies, the main difference in them being that the
hot-trimming dies are left open at the front to clear the sprue
that connects the forging to the bar. Either type of die maybe made solid or in sections, as found most convenient.
FORGING DIESSerial 1682 Edition 1
EXAMINATION QUESTIONS
(1) What is a drop forging?
(2) What is the joint Hne of a pair of dies?
(3) In what two ways may the side thrust of dies be
balanced ?
(4) What are the names of the four recesses that may be
used in dies?
(5) What is the fin?
(6) What are the usual dimensions of the flash ?
(7) What is the sprue?
(8) What is the gate?
(9) How is the fin removed?
(10) What is the purpose of the back flash?
(11) What is meant by a two-operation job?
(12) What is the reason for making a long forging, such as
a spanner wrench, in two operations?
(13) What are heading machines principally used for?
(14) When bending elastic materials cold in a bulldozer,
what special allowance must be made in the dies?
(15) What are wing dies?
§54
2 FORGING DIES §54
(16) What materials are used for making dies?
(17) What is meant by dishing?
(18) Why are two spindles used on a die-sinking machine?
(19) What is the object of planing the die block on the front
and side ?
(20) How are lead proots made ?
Mail your vrork on this lesson as soon as you havefinished it and looked it over carefully. DO NOTHOLD IT until another lesson is ready.
SPECIAL FORGING OPERATIONSSerial 1691 Edition 1
SPECIAL FORGING EQUIPMENT
HEATING FURNACES
1. As heating is necessary in all forging work, suitable
furnaces must be provided in connection with forging opera-
tions. The form of the furnace varies with the nature, size,
and quantity of work to be heated, and with the nature of the
fuel used ; in many cases, one form can be used for several classes
of work, but in other cases each class of work requires its own
special form of furnace. Gas-fired or oil-fired furnaces are
now preferred to those fired with coal or coke, because they can
easily be controlled so as to maintain a more uniform heat.
In all heating ftunaces, the air supply should be so regulated
as to produce incomplete combustion in the part of the furnace
where the heating is done; in other words, there must be no
excess of air, as such excess will oxidize the metal. In the
case of heating furnaces using solid fuel, it is necessary to pro-
vide for the admission of air beyond the heating chamber, so
as to bum the gases completely, if it is desired to prevent the
escape of smoke from the chimney.
2. Small Coke Furnace.—For heating the ends of bars
to be worked under drop hammers or in forging machines, a
small coke furnace, like that shown in Fig. 1, is frequently
used. This fiunace is enclosed in cast-iron plates, the front
and back plates a and h being bolted to flanges on the side
plates c and d. The grate bars e are supported on bearing bars
placed in the furnace lining, which is made of firebrick. The
COPYRIGHTED SY INTERNATIONAL TEXTBOOK COMPANY. ALL RIGHTS RESERVED
§55
SPECIAL FORGING OPERATIONS 55
ashes are removed from the ash-pit through the door /. The
blast pipe is generally inserted into the ash-pit through an
opening in the plate b, and a pressure of from 4 to 12 ounces
is maintained in the pit. A bed of coke is kept on the grate
bars and the material to be heated is placed on the coke. The
opening g through which the work is placed in the furnace is
usually closed, or partly closed, by a firebrick-lined door,
sliding between the vertical guides shown at the right and left
of the door. The gases escape through a flue connected with an
opening in the plate b. While the work is being heated, the
Fig. 1
door is kept closed as much as possible, to prevent any inrush
of cold air over the top of the fire. The door is also usually
provided with a counterbalance so that it can be raised or
lowered with ease.
3. Reverberatory Furnace.—For heating large work, a
reverberatory furnace is usually employed. The work is placed
on the hearth and heated by the hot gases passing over it, and
the heat reflected from the roof, which is a firebrick arch. In
some cases, the roof is arched in such a way as to focus the
heat on some part of the hearth. In a reverberatory furnace,
55 SPECIAL FORGING OPERATIONS
it is necessary to construct the lining of the furnace of firebrick
laid in fireclay. A furnace of this type may use coal, oil, or
gas, and for some classes of work wood; but good bituminous
coal is the fuel most commonly employed. The fuel is usually
burned with forced draft, the bed being kept deep enough to
insure a slightly smoky flame, which indicates incomplete com-
bustion. This makes it certain that oxidation will not take
place from air passing through the grate.
4. A longitudinal section of a furnace used in heating work
for a steam hammer is shown in Fig. 2. The coal is thrown on
the grate g through the fire-door opening h, which is so placed
Fig. 2
that a suitable depth of fire can be maintained between the grate
bars and the bottom of the door. The hot gases pass over the
bridge wall w, and bum in the chamber s, the waste gases escap-
ing through the flue k into the stack. The ash-pit is shown at /.
A plan view of the fiimace is shown in Fig. 3, a side view in
Fig. 4, and an end view in Fig. 5 (a), while (6) shows a section
crosswise through the hearth. Corresponding parts in these
different views are given the same reference letter. The furnace
has three doors c, d, and e on one side, and the door / and the
fire-door h on the other, the door / being opposite the door d.
This is a great convenience in heating long pieces of work, which
are allowed to extend through both openings. All the openings
SPECIAL FORGING OPERATIONS 55
through which work is put into the furnace are closed by doors
lined with firebrick slabs and suspended by chains from counter-
balanced levers. They are raised and lowered by the handles p,
ftnd the weights n serve to hold them in any desired position.
013
§55 SPECIAL FORGING OPERATIONS
5. The bed, or hearth, of the furnace is usually made of
clean, sharp silica sand tightly rammed to nearly the shape of
the hearth. A fire is then placed on the grate and kept burning
until the sand on the surface melts and forms a smooth glassy
hearth. Sometimes clay is mixed with the sand.
In heating work, sand is very frequently used as a flux to
carry off any iron oxide that is formed on the surface of the
metal. Iron oxide also attacks the surface of the hearth, form-
ing a fusible slag with it. This slag flows into the slag pot
Fig. 6
through an opening at the foot of the stack, toward which the
hearth slopes. A blast of from 4 to 12 ounces is supplied to the
fire by the blast pipe t, Figs. 3, 4, and 5 (a), which is attached
to one end of the ash-pit. Usually, the blast is obtained from
the fan that furnishes blast for the forges.
In some cases, the counterweights for the doors are placed
at the side of the furnace, so as to leave the top clear. Aboiler may then be set above the furnace, and the heat from the
waste gases utilized to furnish steam for steam hammers, for
engines driving ^he fans, etc., the gases being led up under the
boiler before they pass up the stack and are allowed to go to
waste.
SPECIAL FORGING OPERATIONS 55
6. Double-Decked Reverberatory Furnace.—In some
shops where a variety of work is done and yet where there is
Fig. 7
not enough heavy forging to warrant the installation of a large
reverberatory furnace, the double-decked reverberatory furnace
shown in Figs. 6 and 7 will be
of service. Fig. 6 shows a sec-
tion along the line efgh of
Fig. 7, and Fig. 7 shows a sec-
tion along the line mn o p oi
Fig. 6; the same reference let-
ters designate the same parts
in both illustrations. In this
furnace, the grate g, ash-pit /,
fire-door i, ash-pit door k, and
blast-pipe connection q are ar-
ranged as in the reverberatory
furnace already described.
When the Jflame passes over
. the bridge wall h, it enters a
O) relatively small chamber with
a hearth u, on which is placed
the work that is to be heated
to a high temperature. After it passes over the hearth u, the
flame passes through the openings c to the lower hearth v, and
Fig. 8
§55 SPECIAL FORGING OPERATIONS 9
thence through the openings, or flues, / to the chimney y. The
lower hearth v is used for heating work for tempering, anneal-
ing, case-hardening, etc.
7. The door for the upper hearth, which is on one side of
the furnace, is not shown in Fig. 6; and the door ; for the lower
hearth is on the other side. The slag hole 5 is at the base of
the chimney. The de-
tailed arrangement of
the furnace doors ; for
closing the large open-
ings is shown in Fig. 8.
Each door contains a
smaller door d, which
may be opened to see
the condition of the
work, or throughwhich small pieces
may be introduced.
The main doors are
counterbalanced by
weights IV. The ad-
vantage of placing the
fire-door at one side of
the furnace is that the
fire can be spread more
evenly than with the
door at the end of the
furnace, since the coal can be raked along the length of the
bridge wall so as to maintain an even fire at all points.
8. Furnace for Long Work.—In shops where long pieces,
such as angles and other structural shapes, must be heated, a
furnace of the form shown in Fig. 9 will be found useful. It
consists of a cast-iron pot, or box a, which serves as an ash-pit
and on the upper surface of which the grate bars are arranged.
The ashes are removed through the door b and the blast is
furnished through a pipe connected at the back of the ash-pit.
Directly above the cast-iron box a, which is supported on
Fig 9
10 SPECIAL FORGING OPERATIONS § 55
cast-iron legs c, is a section supported by the plates d and e,
which are held in place by bolts. Above the plate d is an
angle iron/, which protects the front edge of the furnace. Theback wall and a part of the ends of the furnace are built up with
brick g, and the cover or roof is made of several firebrick slabs
held together by iron binders h ; a coke fire is maintained in the
furnace.
9. Long work may be laid so that its ends project througft
the open ends of the furnace, permitting it to be heated the
whole length of the fire. This furnace will be found especially
useful in heating long angle irons in the center for bending.
When curved or irregular pieces must be heated, the cover is
frequently lifted off while the work is being placed in the
furnace and then replaced during the heating. If large nvim-
bers of short pieces are to be heated on the ends only, the
pieces are laid across the angle iron /, Fig. 9, and allowed to
project into the fire. When the furnace is not in use for heating
long work, the openings in the ends can be closed temporarily
with firebrick. Such a furnace as this is generally used in a
large open building where structural shapes are put together,
and hence the escaping gases are not objectionable. If the
furnace is to be used indoors in winter, an exhaust pipe to carry
away the gases can be arranged at the back of the furnace.
10. Special Heating Furnace for Higli Tempera-tures.—^When a large amount of work is to be heated, it is
often convenient to make the process continuous by using
a conveyer that will carry the work slowly through the fur-
nace, the cold pieces being placed on the conveyer at one
end of the furnace and removed at the other end properly
heated for forging. Such a ftimace is shown in Fig. 10. The
conveyer consists of a series of small trucks a that carry fire-
clay blocks b on which the work c is placed at one end / of
the furnace and carried through to the other end, by which
time it is thoroughly heated. The trucks then return empty
along a track under the furnace, to be loaded again with work.
A metal casing e surroimds the blocks b on the return, so as to
prevent undue loss of heat.
12 SPECIAL FORGING OPERATIONS 55
11, The fiimace d, Fig. 10, is a rectangular iron box lined
with firebrick, and is heated by gas burners g, placed on the top
of the furnace and supplied by a pipe h extending along the side.
The trucks do not enter the furnace, because the temperatures
are too great to be withstood by cast iron, but the fireclay
blocks project into the flame.
The biimers can be controlled separately, so that any desired
temperature may be obtained. They are placed so as to direct
the flame toward the end /, so that as the work enters the fur-
nace it is first heated by the blocks on which it rests, then by
the hot gases, and finally by the flame under which it passes.
MISCELLANEOUS OPERATIONS AND DATA
FORGING STRUCTURAL SHAPES
12. Bending Angles.—With the more general use of
structural shapes and plates, such as angle iron, I beams, deck
beams, etc., it has become necessary to bend them into various
shapes or forms. Where a considerable amount of this class of
Fig. 11
work is to be done, bending plates, Fig. 11, are used; these
are large surface plates with holes in their surfaces, in which
are fixed the dogs and clamps for holding the work. For
bending the angle a to the desired curve, the form h is first
55 SPECL\L FORGING OPERATIONS 13
clamped to the bending plate by means of a dog- c; the end of
the angle is also held down by means of a dog d. These dogs
are simply curved pieces of metal that are spnmg into the
holes in the plate and driven down into contact with the work.
13. The angle is bent around the form by means of a
moon e, Fig. 11. which is a crescent-shaped piece of metal
secured to a long arm and provided with a pin or tongue near
the end. This tongue is dropped into one of the holes in the
plate, and the angle is bent by sweeping the moon around. Of
course, as the angle bends, the outer edge of the projecting
flange will be stretched and drawn thin, and care must be taken
to see that it does not buckle. By careful handling, very sharp
curves can be bent in this way. Fig. 12 (a) shows an angle
Fig. 12
that has been bent into a circle and afterwards welded, and{b) shows an angle bent to form the frame for a door; both of
these were bent arotind forms by the use of moons. Large
bending floors, made up of several bending plates laid side byside, are used in bending very large work. Forms made of iron
or steel bars bent to the proper shape are clamped on the bending
floor with dogs, as shown in Fig. 13. The piece to be bent is
then forced around the form by means of moons.
14. Welding- Angles.—In some classes of work, it is often
necessary to bend angles and other structtiral shapes to such
sharp angles that it is impossible to make the metal flow to the
desired form. Four examples of this nature are shown in
Fig. 14. In making the piece shown in (a), it is necessary to
207—9
14
§55 SPECIAL FORGING OPERATIONS 15
cut out a piece of the inside flange of the angle at the point a,
so that the angle before bending will appear as shown in (e).
After bending, the faces b and c are brought together and
welded. In like manner, the outer corners d and e of the
piece in (6) must be split and pieces welded in after bending.
Similarly, pieces must be cut out of, and others welded into, the
webs of the pieces shown in (c) and (d). If the parts are kept
^ ^^\__—1^—
I
Fig. 14
clean and the fire in proper condition when making these welds,
no flux is necessary, as the flux tends, in many cases, only to
eat away the surface of the metal.
15. Bending Structural Shapes.—Channels, I beams,
deck beams, and other structural shapes are bent by using
proper forms. In some cases, it is necessary to have an outline
of the sectional shape formed in the side of the former used.
16 SPECIAL FORGING OPERATIONS 55
In all work on structural shapes, care must be taken to see
that the steel is not heated very far above the point of recales-
cence, or 1,250° F., except for welding; and any pieces that
must be heated to a higher degree should be allowed to cool
after they are forged to shape, and then heated to just above
the point of recalescence, or 1,250° F., and allowed to cool
once more. This will relieve the stresses and restore the fine
texture of the metal and insure the greatest possible strength
in the piece.
16. Bending Plates.—In bending plates into irregular
forms, they are first brought roughly to shape under suitable
Fig. 15
presses and are then secured to the bending floor by means
of dogs, as shown in Fig. 15. Suitable bars or supports are
placed at the sides, and the plates formed to a templet by the
use of wooden mauls, three of these mauls being shown on
the bending floor in Fig. 13. By careful work in this way, a
plate can be formed to any required shape.
55 SPECIAL FORGING OPERATIONS 17
EFFECT OF REPEATED HEATING ON METAL
17. Effect of Repeated Heating on Cast Iron.—If
cast iron is heated repeatedly, it will increase in size with
each successive heating; the volume has been increased as
much as 40 per cent. This heating opens the grain of the
metal and weakens it very greatly. Hence, gray-iron castings
should not be exposed to repeated heatings if it is desired that
they retain their form and size. This increase of volume of
the metal has, however, been put to practical use for increasing
the size of parts that have become worn to such an extent that
they no longer fill the space for which they were originally
intended. To do this, the pieces are packed in air-tight boxes
or tubes, heated to a dull red, and then allowed to cool.
18. Effect of Repeated Heating on Wrought Iron
or Steel.—It has also been found that repeated heating of
wrought iron or low-carbon steel reduces the volume slightly.
Advantage may be taken of this shrinkage in cases where it is
necessary to reduce slightly the diameters of holes in forgings,
or the diameters of rings. If such pieces are heated to a dull
red and allowed to cool slowly, or even if they are quenched
in water, they will usually be found to have decreased slightly
in size.
ESTIMATING STOCK
19. General Rule for Finding Stock.—The work of
the blacksmith is such that he is frequently required to esti-
mate the amount of stock of a certain size needed to make a
certain piece of work. Usually a dimensioned sketch or drawing
of the required piece is given to him and he must then calculate
the length of bar stock that must be cut off to make the piece.
To accomplish this, the following riile may be used:
Rule.— Calculate the volume of the required piece in cubic
inches and divide it by the area, in square inches, of the stock
from which the piece is to be made. The quotient will be the required
length of stock, in inches.
18 SPECIAL FORGING OPERATIONS § 55
If the piece to be forged is not of the same shape throughout,
it may be considered as being made up of several parts. The
volumes of these separate parts should be calculated, and their
sum will then be the total volume of the piece.
The foregoing rule does not include any allowances for losses
during the forging operation, nor for waste due to the trim-
ming off of rough ends so as to obtain a sound forging. Such
allowances cannot be fixed by any general rule, because they
vary according to the nature and size of the work and are
determined largely by experience.
20. In the calculation of the volume of a piece of work of
round or rectangular section, the area of cross-section is used.
To save time and labor, the cross-sectional areas of round
and square steel bars of various sizes are given in Table I at
the end of this Section. The first column gives the side of the
square bar or the diameter of the round bar, in inches; the
second and third columns give the weights per foot of square
and round bars, respectively, of the different sizes; and the last
two columns give the areas corresponding to the various sizes of
square and round bars. Tables II and III give simply the
weights per foot of square, round, and flat wrought-iron bars.
These two tables, as well as the first three columns of Table I,
may be used to find the weight of a bar of iron or steel of a
given size and length.
For example, suppose it is desired to know what length of
stock 1| inches square will be required to make a piece 12 inches
long, 2 inches wide, and f inch thick. The volume of the
required piece is 12X2Xf = 9 cubic inches. According to
Table I, the area of cross-section of a bar 1| inches square is
2.25 square inches. Hence, applying the rule of Art. 39, the
length of stock required is
9-4-2.25 = 4 inches
21. General Rule for Drawing or Upsetting.—The
work of the blacksmith frequently involves drawing and
upsetting operations. For example, he may find it necessary
to draw a piece of square stock to a smaller square, or to a
round section, or perhaps to a rectangular shape, and he may
§ 55 SPECIAL FORGING OPERATIONS 19
wish to know how long the piece will be after it has been drawnout. On the other hand, it may be necessary for him to upset
a piece to a larger cross-section, and he may wish to calculate
the finished length. No matter whether the operation is
drawing or upsetting, or whether the stock is round, square, or
,any other shape, the general rule to be used is as follows:
Rule.— Calculate the volume of the original piece in cubic
inches and divide it by the area, in square inches, of the cross-
section to which it is to be forged. The quotient will be the final
length of the piece, in inches.
If the piece of stock is to be forged to different shapes andsections at different points, it should be considered as being madeup of several parts, and the length of each shou-ld be calculated
by the foregoing rule.
The method of using this general rule can best be illustrated
by means of examples and their solutions. To begin with a
simple case, suppose that a piece of iron 1 inch square and2 inches long is drawn out to a bar | inch square, and that the
final length of the piece is to be calculated. The volume of
the original stock is 1X1X2 = 2 cubic inches. The cross-
section of a bar | inch square is 2X1 = 1: square inch. Then,
according to the rule, the length of the piece, when drawn out,
is 2-T-i =fX^= 8 inches.
22. As a further example, suppose that the original piece
of stock is to be drawn down to a round bar | inch in diameter.
The area of cross-section of this round bar would be .4418 square
inch, according to Table I. Then, according to the rule of the
preceding article, the length of the round bar would be 2-^ .4418
= 4.53 inches, or approximately 4|-g- inches.
Again, suppose that the cross-section of the finished piece
was to be rectangular, and to measure 1\ inches by f inch.
The area of such cross-section is l4X8=fXf = ff square inch.
The length of the finished piece, therefore, would be 2-hff= fX|-| = f|-= 2.56 inches, or approximately 2j^ inches.
As a further example, suppose that a piece of round bar
1^ inches in diameter and 3 inches long is to be drawn down to
a rectangular piece 2 inches by | inch in section and that the
20 SPECIAL FORGING OPERATIONS 55
length of the rectangular piece is to be found. According to
Table I, the cross-sectional area of a round bar 1| inches in
diameter is 1.7671 square inches. The length of the piece of
l|-inch stock is 3 inches, and therefore the volume must be
1.7671X3 = 5.3013 cubic inches. The cross-sectional area of
the rectangular piece is 2X^ = 1 square inch. Applying the
rule of Art. 21, therefore, the length of the rectangular piece
will be 5.3013 -T- 1 = 5.3013 inches, or about 5j^ inches.
23. Stock Required for a Y.—-Suppose that it is desired
to find the length of stock, | inch by 1| inches in section, required
Fig. 16
to form a Y having the dimensions shown in Fig. 16 (a). The Y
may be considered as being composed of three equal arms a, b,
and c, each ^ inch square in section and 2j inches long. The
volimie of each of these pieces is ^X^X2j = 3^ cubic inch, and
the volume of all three is 3Xi^ = f6 = lf6 cubic inches. The
cross-sectional area of the stock to be used is |Xl| =iXf= f square inch. The length of stock required, therefore,
according to the rule of Art . 2 1 , is 1ii h- f = fiX 3 = I = 2| inches,
as shown in (b) . This calculation, it will be observed, does not
take account of the small amounts of material at d, e, and /in (a) ; consequently, the calculated length, 2j inches, will not
55 SPECIAL FORGING OPERATIONS 21
Fig. 17 A
give sufficient stock. However, the amount of material at d, e,
and /is very slight, and in small work may usually be neglected.
If it must be allowed for, the length
of the stock may be increased ac-
cording to the judgment of the black-
smith, in this case about | inch,
making the piece of stock 2| inches
long. The stock is first split as in-
dicated by the dotted line in {b), for
two-thirds of its length, after which the arms are spread and the
three sections are drawn down to the shape and size given in (a).
24. stock Required for Square Bend.—If a piece of
stock of uniform section is to be bent, as shown in Fig. 17, so
that the two legs shall be of certain required lengths and at
right angles to each other, the length of straight bar required
may be calculated by the following rule
:
Rule.— To the length of one leg, measured on the inside of the
bend, add the length of the other leg, measured on the outside of
the bend, and to their sum add -| inch. The result will be the
length of straight bar required.
Suppose a piece of iron ^ inch square is to be bent to the size
and shape indicated in Fig. 17 and it is desired to know the length
of straight stock required. The length of one leg, measured on
the inside of the bend, is 3 inches, and the length of the other,
measured on the outside of the bend, is 2^ inches. By the rule,
the length of straight stock required is 3-f2|+| = 5f inches.
25. Stock Required for Bolt.—A bolt may be made bycutting off a piece of round bar of sufficient length and upsetting
_Ji ^
Fig. 18
one end to form the bolt head. Suppose that a bolt f inch in
diameter and 4 inches long is to be made from f-inch round
22 SPECIAL FORGING OPERATIONS § 55
stock, and that the length of stock is to be found. The bolt
will have the dimensions shown in Fig. 18. It may therefore
be considered as being made up of a cylindrical shank f inch
in diameter and 4 inches long, and a head IJ inches square
and f inch thick. Since the shank is of the same diameter as
the stock, f inch, and 4 inches long, it will require a piece of
stock 4 inches long. The volimie of the bolt head is IjXllXf = 1.17 cubic inches. The area of f-inch round stock is
.4418 square inch, according to Table I. The stock required
for the head, therefore, is 1.17^.4418 = 2.65 inches, or approx-
imately 2| inches. Then, the total length of stock required
is 4+2f = 6f inches.
If the bolt is to be made by drawing down a piece of square
stock, the same method may be followed. The cylindrical
shank f inch in diameter has an area of .4418 square inch,
§ 55 SPECIAL FORGING OPERATIONS 23
each end must therefore be calculated. The area of a circle
2f inches in diameter is 4.4301 square inches, according to
Table I, and that of a circle 2| inches in diameter is 6.4918 square
inches. The volume of the part b, therefore, is 4.4301X4^= 19.9 cubic inches, and of the part c is 6.4918X34 = 220.7 cubic
inches. The total volumie of the parts b and c is 19.9+220.7
= 240.6 cubic inches. The area of 4f-inch stock is 14. 186 square
inches; hence, by the rule of Art. 19, the length of 4j-inch
stock reqtdred for the ends is 240.6 -^ 14. 186 = 17 inches, nearly.
To this must be added the 8 inches required for the part a,
giving a total of 25 inches as the length of stock required for
the forging.
27. Another way of working out this problem is to use
the weights per foot of round steel of different sizes, as given
in Table I. As before, let the shaft be considered as being
composed of three cyHndrical parts. The part b is 4| inches,
or 4|-^12 = f foot, long, and 2f inches in diameter. Accord-
ing to Table I, the weight of 1 foot of 2f-inch round steel is
15.06 poimds; hence, the weight of f foot is |X 15.06 = 5.6
pounds. The part c has a length of 34-^12 = 2f feet, and its
weight is 21x22.07 = 62.5 pounds. The total weight of the
ends b and c, then, is 5.6+62.5 = 68.1 pounds. The stock to
be used is 4j inches in diameter and weighs, according to Table I,
48.24 pounds per foot. The length of stock required for the
ends, therefore, is 68.1-4-48.24 = 1.412 feet, or 12X1.412 = 16.94
inches, or approximately 17 inches, as before. The middle
part a requires 8 inches of stock. Therefore, the total length
of stock required is 17+8 = 25 inches.
28. Stock Required for Crank-Shaft.—Suppose that
a steel cranl<-shaft is to be forged from a rough ingot and that
the completed forging is to have the form and size shown in
Fig. 20 (a). The parts a and b, from which the craiiks are
formed, as indicated by the dotted hues, are 29 inches wide and
13 inches thick; therefore, the first step in forging is to draw
the ingot down t« a bar of rectangular cross-section 29 inches
by 13 inches. The parts c, d, and e are then made by drawing
down the rectangular bar at the proper places. The length of
24 SPECIAL FORGING OPERATIONS 55
rectangular stock required is equal to the volume of the crank-
shaft forging, in cubic inches, divided by the area of the rec-
tangular cross-section, in square inches. The volume of each
of the parts a and b is 23X29X13 = 8,671 cubic inches, and the
volume of both is 2X8,671 = 17,342 cubic inches. The parts c,
d, and e are of the same diameter, 10 inches, and their cross-
section is therefore 78.54 square inches, according to Table I.
The combined length of the three parts is 24+58+36= 118 inches, and the total volume of the three is 78.54X118= 9,268 cubic inches. The volume of the crank-shaft forging,
then, is 17,342+9,268 = 26,610 cubic inches. A section
O
O7
—z.?'-^ . I- i
Ia
-sj"—4^
T
T^ijv
(a)
-13"—h-^H^
r.'
i
9\\
-23" f /^a''+ .7^^
k^(b)
Fig. 20
29 inches by 13 inches contains 377 square inches. The length
of stock of this size, therefore, is 26,610^377 = 70.6 inches. Toallow for fillets and for trimming the ends, the piece of rec-
tangular stock should have an over-all length of at least
76f inches, as shown in (6). Practically, the piece would be
made 78 inches, or 6| feet long.
29. After a sufficient length of rectangular stock has been
drawn down from the ingot, as shown in Fig. 20 (6), it must be
marked off properly, so that the parts c, d, and e in view (a) can
be forged. The part c has a volume of 78.54X24= 1,885 cubic
inches. The length of rectangular stock required for this part
§ 55 SPECIAL FORGING OPERATIONS 25
is 1,885-^377 = 5 inches. As the end of the stock is rough and
must be trimmed off, the measurements are made from a point
several inches from the end, indicated by the dotted line/in (b).
From the Hne / a distance of 5 inches is laid off, marking the
stock required for the part c. Next, a distance of 23 inches is
laid off, marking the stock required for the crank a. The part d
has a volume of 78.54X58 = 4,555 cubic inches and requires
a length of stock equal to 4,555-^377 = 12| inches; hence, a
distance of 12| inches is laid off, as shown. This is followed
by another section 23 inches long, for the crank b. The part e
has a volume of 78.54X36 = 2,827 cubic inches and requires
2,827-^ 377 = 7| inches of stock, which is marked off at the
right. After the stock has been marked off, as shown, it is
heated, and a hack is used to notch it as indicated by the
V-shaped cuts. These notches must be square on the faces
that form the sides of the parts a and b, and their depth must be
a little less than 17| inches, which is the length of the crank,
measured from the side of the shaft to the outer end. In this
particular case, the notches cut by the hack wotild be between
17 and 17j inches deep. The metal at g, h, and i is then forged
to a circular shape, 10 inches in diameter, thus forming the
parts c, d, and e.
30. Avoiding Waste of Stock.—^When cutting pieces of
material for forging operations, the bar stock selected should
be of such length as to enable the pieces to be cut with little or
no waste. To illustrate this point, suppose that a number of
pieces of steel 9 feet long are required for wagon tires; also,
suppose that the supply of stock of the proper size consists of
two lots of bars, one lot 10 feet long and the other 18 feet long.
If the tires are cut from the 10-foot bars, there will be a waste
end 1 foot long cut off each bar ; but if the 18-foot bars are used,
each will furnish stock for two tires, without any waste. Hence,
it would be preferable to use the 18-foot bars. In addition, less
cutting would be required to obtain the required nvimber of
tires, since each cut would give two pieces; whereas, if the
shorter bars were used, each cut would give only one piece,
besides causing a waste of 1 foot.
26 SPECIAL FORGING OPERATIONS 55
Fig. 21
31. stock Required for Circular Ring.—When a
piece of straight stock is bent to a cvirve, the material at the
outer side of the bend is stretched and that on the inner side is
compressed. The length of the center line of the piece, how-
ever, changes little, if any. If it is desired to find the length
of straight stock needed to form
a circular ring, the following rule
should be used:
Rule.—To find, the length oj
straight Stock required for a circular
welded ring, multiply the diameter
of the ring, measured from center
to center of stock, by 8.I4I6, and to
the product add half the thickness of
the stock.
For example, suppose that a ring
of the size shown in Fig. 21 is to
be made and that the length of straight stock required for
it is to be found. The inside diameter of the ring is 4 inches,
and the diameter of the stock is f inch ; hence, the diameter from
center to center of stock is 4f inches. Then, applying the rule,
the length of straight f-inch stock required is (4fX3.1416)
+ (i Xf ) = 15+f = 15f inches. The addition of half the thick-
ness of the stock is made to allow for loss of material in welding.
The same rule holds true for
square, hexagonal, or oval stock
bent to a circular ring.
32. The link shown in Fig. 22 is
known as a figure-8 link and is bent
to shape without welding. It maybe considered as being made up of
two circular rings, since each end of the link has an approximately
circular form ; and as the link is not welded, no allowance for weld-
ing need be made. The rule to be used, therefore, is as follows
:
Rule.—Considering each end of the link as a circular ring,
multiply the diameter of the ring, measured from center to center
Fig. 22
§ 55 SPECIAL FORGING OPERATIONS 27
of stock, by 3.I4I6, and then multiply that product by 2. The
result is the length of stock required for the figure-8 link.
Suppose that the length of straight stock for the link shownin Fig. 22 is to be found. The inside diameter of each end
is 2X 1^ = 1 inch, and the stock is ye inch in diameter. Thediameter of the ring from center to center of stock, therefore,
is 8+1^ = if inch. Then, applying the rule, the length of
stock required for one end is ||-X3.1416 = 2.95 inches, or nearly
3 inches, and for the whole link the stock required is 2X3= 6 inches.
33. stock Required for Chain Link.—A chain link of
the form shown in Fig. 23 consists of two equal semicircular
ends joined by straight sides. The amount of stock needed
for the sides is equal to twice the
length of one side of the link ; and
as the two ends together form a
circle, the amount of stock re-
quired for them, including the
allowance for the weld, may be
calculated by the rule of Art. 31.
For example, suppose that the
link is to have the dimensions
marked on it in the illustration
and that the length of straight stock required for it is to be
found. The length of f-inch round stock required for the twostraight sides is 2Xf = lj inches. The two semicircular ends
together form a ring whose inside diameter is 2Xi^ = | inch,
and whose diameter from center to center of stock is |+ |= 1 inch. According to the rule of Art. 31, therefore, the stock
required for the two ends is (lX3.1416)+ (^Xf) =3i+i^= 3^^ inches. The total length of straight stock needed to
form the link, then, is l4+3i^ = 4]^ inches.
34. stock Required for Irregularly Curved Work.If a piece of work is made up of one or more irregular bends,
so that none of the rules previously given can be used to find
the length of straight stock needed, then the length of the
center line must be found; for it has already been stated that,
28 SPECIAL FORGING OPERATIONS § 55
when a bar is bent, the center Hne remains practically unchanged
in length. If the length of the center line is found, therefore,
the length of straight stock needed will be known. One way of
doing this is to take a piece of soft wire of sufficient length and
bend it to the shape of the desired piece along the center line.
When straightened out, the length of this wire will be the
length of straight stock required. Another way is to markthe center line on the work and then with a pair of dividers set
to a convenient dimension, to step off divisions along the center
line from one end to the other. The number of divisions thus
obtained multiplied by the distance between the points of the
dividers is the length of the center line, and also of the stock
required.
35. In case the amount of upsetting is great, or if the piece
is to be machined to size after forging, the amount of stock
required is greater than the voliime of the finished piece. Sup-
pose, for example, that a cylindrical cutter blank is to be made,
the finished size of which is to be 7| inches in diameter and
Ij inches thick; and, further, suppose that the available stock is
4 inches in diameter. It will be necessary to cut off a piece of
this 4-inch stock and upset it to a size larger than the finished
blank, so that there will be ample allowance for machining.
In the problem assumed, the rough forging would be upset to
a diameter of 8 inches and a thickness of 1^ inches. Thecross-sectional area of a forging 8 inches in diameter is 50.266
square inches, according to Table I. Then the volume of the
forging is 50.266X12=75.4 cubic inches. The cross-sectional
area of 4-inch round stock is 12.566 square inches. Then,
according to the rule of Art. 19, the length of stock required
is 75.4 -^ 12.566 = 6 inches.
36. Finding Volume by Water Displacement.—It
may happen that a forging of irregular form is made as a
sample or specimen piece, and that it is then desired to know the
amount of stock required to make duplicate pieces. If the work
is of very irregular shape, so that the calculation of its volume
is apt to be difficult, the desired result may be obtained in
another way. A tub with straight sides is filled to overflowing
§55 SPECIAL FORGING OPERATIONS 29
with water. Then the piece whose volume is to be found is
lowered into the tub until it is entirely submerged in the water.
Some of the water will thus be displaced and flow over the edge
of the tub. The piece is next lifted out, and it will be found
that the water level is then below the edge of the tub. The
volimie of water thus forced out of the tub represents the voliime
of the piece, and is equal to the cross-sectional area of the tub
multiplied by the distance from the top of the tub to the surface
of the water. If the piece that is lowered into the water is a
machined forging, the volume found will be the volume of the
finished piece, and this will need to be increased by a certain
allowance to obtain the volume of the rough forging. The
length of stock required can then be found by the rule of
Art. 19. To have this
method give reasonably
accurate results, the tub
or vessel used should be
just large enough to con-
tain the piece of work
when fully submerged.
K--3"H
k"+-
FiG. 24
37. As an example,
suppose that it is desired
to know what length of
5|-inch round stock will
be required to make the rough forging from which the finished
piece in Fig. 24 is machined. Let it be assumed that, when the
finished piece has been submerged in a filled tub 20 inches in
diameter and withdrawn, the water level in the tub is xl inch
below the edge. The volume of water that must have been
displaced by the piece is then 202X.7854 Xf| = 294.5 cubic
inches. To make allowance for finish, the rough forging must
be larger than the finished piece. With careful workmanship,
an allowance of 5 per cent, in volume is sufficient; that is, the
voltime of the rough forging is taken as 5 per cent, more than
that of the finished piece. The rough forging must therefore
contain 294.5+(.05X294.5) = 294.5+ 14.7 = 309.2 cubic inches.
The stock used is 5| inches in diameter and has a cross-section
207—10
so SPECIAL FORGING OPERATIONS 55
of 23.8 square inches. The length of stock reqiiired, therefore,
is 309.2^23.8 = 13 inches.
38. Shrinlving on a Liiik.—Machine parts are often
held together by links or bars shrunk on. An example of this
construction is shown in Fig. 25,
in which a is a steel link that is
shrunk on the bosses b and c,
which form projections on the
pieces d and e, respectively.
The link is made of such size
that, when heated to a red heat,
it will just slip over the bosses b
and c. As it cools, it shrinks,
and the parts d and e are thus
held together very tightly. Theincrease in the length and width
^^^' ^^of the link while being heated to
a red heat is slight, amounting to a very few hundredths of an
inch; consequently, it is useless to calculate the size of the cold
link with a view to making allowance for heating and shrinking.
The link is simply made smaller than the inside dimensions
marked, and is heated to redness and tried on the bosses. If it
will not go on, it is drawn a little, heated, and tried again, and
these operations are re- „
peated until the red-hot link
can just be slipped over the
bosses.
Fig. 26
39. Stock Requiredfor Busliing.—If a cylin-
drical steel bushing is to be
forged from a piece of solid
round stock, a hole is first drilled lengthwise through the center
of the stock. The piece is then heated, a mandrel is inserted,
and the work is forged to the desired size, the size of the mandrel
being changed as the hole grows larger. Suppose that the rough
forging of a bushing is to have the dimensions shown in Fig. 26
;
also, that the length of stock to be used is 6 inches, that a 1^-inch
§ 55 SPECIAL FORGING OPERATIONS 31
hole is to be drilled in it, and that its diameter is to be foiind.
The cross-section of the rough forging is the difference between
the area of a 6-inch circle and the area of a 4-inch circle, or,
according to Table I, 28.274-12.566 = 15.708 square inches, and
the volume is 6X15.708 = 94.248 cubic inches. The original
piece of stock must contain this amount of steel, and, in addition,
the quantity removed by the drill, which is equal to the volume
of a cylindrical piece 1| inches in diameter and 6 inches long.
According to Table I, the area of a l|-inch circle is 1.7671
square inches ; then thevolume is 1.7671 X 6 = 10.603 cubic inches.
The volume of the stock, therefore, must be 94.248-|- 10.603
= 104.851 cubic inches. The length of the stock is to be
6 inches; hence, its cross-section must be 104.8514-6 = 17.475
square inches. According to Table I, the area of a round bar
most nearly equal to 17.475 square inches is 17.721 square inches
and the diameter corresponding to this area is 4f inches ; there-
fore, a piece of stock 4| inches in diameter and 6 inches long
would be drilled with a l|-inch hole and forged to the size indi-
cated. To keep the length from increasing, the piece must be
upset repeatedly during the forging.
40. Forging Square From Round.—It is often desirable
to know the size of round stock required to produce a square
bar of given size, without upsetting. This can easily be done by
the use of Table I. The area of the desired square is first found,
and then the area of round bar most nearly equal to the area
of the square. The diameter corresponding to the area of round
bar thus found is the size of round bar that can be forged to the
given square without any upsetting. For example, a l|-inch
round bar can be used to give a 1-inch square bar, because the
area of the former is .994 square inch, which is very nearly
equal to the area of the latter, or 1 square inch. Similarly, a
3j-inch round bar will produce a 2|-inch square bar, because
its area, 8.2958 square inches, is approximately equal to the
area of the square bar, or 8.2656 square inches.
41. Stock Required for Forged Ring.—Suppose that
it is desired to know what length of stock 10 inches square
will be required for the rough forging shown in Fig. 27, assuming
32 SPECIAL FORGING OPERATIONS 55
that a circular piece 6 inches in diameter is punched out whenthe stock has been forged to 3 inches in thickness. The forging
is rough and varies from 6 to 7 inches in width, as indicated.
The average width is (6+7)-t-2 = 6| inches, and the average
inside diameter is 30— (2X6^) =30— 13 = 17 inches. The area
of the ring, then, is 30- X.7854-H^X.7854 = 707 -227= 480 square inches. The thickness is 3 inches; therefore, the
volume of the forging is 3X480=1,440 cubic inches. Thecylindrical piece that is punched out, before the ring is put on a
mandrel and forged to size, has an area of 28.274 square inches,
according to Table I, and a vohmie of 28.274X3 = 85 cubic
inches. The volume of stock required, therefore, is 1,440+85= 1,525 cubic inches. The stock is 10 inches square, correspond-
ing to a cross-section of 10X10= 100 square inches ; hence, the
length needed must be 1,525
H- 100 =15.25 inches, or 15iinches.
Fig. 27
42. Cutting Stock With-out Waste .—-It is desirable not
to waste stock, particularly if it
is expensive material. Suppose,
for example, that a bar of tool
steel 7 feet long is to be made into cold chisels, each of which
requires a piece of stock 6| inches long. The length of the bar
is 7X 12 = 84 inches, and as each chisel needs 6j inches of stock,
there will be enough material for 84-^6j = 13ii pieces; that is,
the bar will make 13 pieces 6j inches long, and there will remain
a waste end 2f inches long. This waste can be avoided bydividing it among the 13 pieces, increasing the length of each
slightly. The stock for each piece will then have a length of
84 -^ 13 = Gt^ inches, or almost 6y| inches. Moreover, by divid-
ing the slight excess of stock among the several pieces, the
number of cuts on the bar is reduced by one, thus lessening the
time, the labor, and the wear on the tools.
43, stock Required for Valve Link.—The finished
piece shown in Fig. 28 (a) is a valve link and is used in the
55 SPECIAL FORGING OPERATIONS 33
reversing gear of a steam engine. It is forged from a piece of
steel 3f inches square, the successive steps in the forging oper-
ation being shown in views (b) to (d). The stock is first marked
out, as shown in (b) , the widths a, b, and c being the parts that
form the cii'cular bosses in (a). The stock is then fullered, as
shown in (c), leaving the parts a, b, and c with square sides,
Tf
Lenqfh ofLink on Center Line 3Z^
(a)
h-^l'H
34 SPECIAL FORGING OPERATIONS § 55
have the sizes shown in (d). The completed forging then con-
sists of four parts, each of rectangtdar cross-section. The volume
of the part a is 2jX2|Xli = 6.3 cubic inches. The volume of
the part b is 3|X3|Xli = 15.3 cubic inches. The volume of
the part c is equal to that of a, or 6.3 cubic inches. The main
part d has a volume of 33 X3fX2 = 247.5 cubic inches. Thevolume of the forging, therefore, is 6.3+ 15.3+6. 3-|-247.
5
= 275.4 cubic inches. The area of a bar 3f inches square is
14.063 square inches, according to Table I; hence, the length
of stock required is 275.4-^ 14.063 = 19.58 inches, or 19^ inches,
approximately.
THERMIT WELDING
44. Thermit.—If aluminum in the form of powder or
filings is mixed in the proper proportions with powdered iron
oxide and the mixture is set on fire, the oxygen in the iron
oxide is taken up by the alimiinum ; in other words, the alum
inum bums to oxide of aluminum and the iron in the iron oxide
is set free. The burning of the aluminum is accompanied with
great heat, and the temperature of the mixture is raised to
about 5,400° F. This is considerably above the melting point
of iron; consequently, the effect of the rapid burning is to
produce a quantity of highly heated molten iron, as well as
a slag consisting of oxide of aluminum. The mixture of alum-
inum and iron oxide is known as thermit, and the high temper-
ature set up by its burning, in connection with the molten iron
produced, enables it to be used to advantage in welding broken
forgings and castings. The molten metal produced by the
burning of thermit is called thermit steel.
45. Crucible for Thermit.—Inasmuch as the temper-
ature resulting from the burning of thermit is very high, the
vessel in which the action takes place must be built to withstand
the heat. This vessel, known as a crucible, is shown partly in
section in Fig. 29. The conical sheet-iron shell a is lined with
a thick layer of refractory material b that is strong and able
to resist the effects of high temperature. At the bottom of the
cone is a circiilar iron plate c with a hole at its center. It
§55 SPECIAL FORGING OPERATIONS 35
supports a cylindrical block d of magnesia, which has a tapered
hole through it. In the tapered hole is set the thimble e, which
has the same taper as the hole. The thimble is also made of
refractory material of high grade, because the molten metal is
tapped through it. The opening in the thimble is closed, during
the burning of the thermit, by an asbestos washer /, beneath
which is a scarfed pin g that hangs freely inside the thimble.
On top of the washer
is rammed an iron
disk h, and over the
disk is poured a layer
of sand i.
46. Preparingand Firing Cliarge.
After the plugging ma-terial has been placed
in the small end of
the conical crucible,
Fig. 29, the charge of
thermit / is poured in
and leveled on top.
Then, in the center of
the top surface is
placed a teaspoonful
of ignition powder k,
and two or three matches are set into it, with their heads
upwards. These matches are now set on fire by the flame of
another match, the hand is withdrawn quickly, and the cover /
of the crucible is put in place. The burning of the thermit
charge is violent, and will cause the crucible to vibrate. As
soon as the vibration has ceased, the burning is ended, and
the thermit steel is ready to be tapped. To do this, the lower
end of the pin g, which projects below the crucible, is given a
sharp blow upwards with the flat end of a tapping spade, or flat
iron bar. The asbestos washers and the metal disk are thus
displaced and the molten metal runs out through the hole in
the thimble and is directed into the mold siu-rounding the broken
36 SPECIAL FORGING OPERATIONS §55
part that is to be welded. The crucible may be supported on a
tripod or suspended by a suitable sling.
47. ApplicatlonsofThermit.—When a partof a machine
breaks, a great deal of time and labor may be required to
remove the broken piece and replace it with a new one. If the
break can be repaired without taking the part away or dis-
mantling the machine, a considerable saving results. Thermit
§ 55 SPECIAL FORGING OPERATIONS 37
thermit steel fills the mold, it runs between the ends of the
broken piece, and a part of its heat raises the temperature of
the ends to the melting point. The result is that the ends and
the thermit steel unite in one mass that, when cool, forms a
weld joining the parts of the broken piece.
48. Mold for Thermit Welding.—The mold used in
making a thermit weld must fit snugly over the work and mustbe so shaped that a collar of steel will be formed about the
weld. If the piece is of regular form, as, for instance, a loco-
motive frame, a firebrick mold designed especially for making
the weld may be ptuchased. In Fig. 30 (a) a mold of this kind
is shown assembled. It consists of three pieces a, b, and c,
which are shown separated in (6). The side blocks a and b are
held together by the three bolts d, which pass through from side
to side and have washers under the heads and nuts. Thebottom piece c is clamped to the others by the eye-bolts e,
which fit over two of the bolts d and pass through the straps /.
The joint siirfaces of the firebrick blocks are coated with a
thin layer of fireclay before they are bolted together, to insiire
tight joints. The channel g is the pouring gate, which leads
the molten steel to the bottom of the break and allows it to
rise around the ends to be joined. The opening h serves as a
riser and the groove i forms the collar of metal around the
weld. The rectangular frame extends through the opening /,
and the joints are luted with fireclay.
49. Welding Locomotive Frames With Thermit.By using thermit it is often possible to repair broken locomotive
frames without removing them; that is, the welds are madewhile the parts are in place. Suppose, for example, that a
frame breaks at one of the upper corners of a jaw. The first
thing to do is to remove enough parts near the fracture so that
it will be accessible and so as to make room for a mold about
1 foot wide. Next, a series of holes | inch or 1 inch in diameter,
depending on the size of the frame, should be drilled along the
line of the break, overlapping one another as shown at a,
Fig. 31 (a), and the metal should be chipped away, leaving a
gap between the ends. The parts of the frame should then be
38 SPECIAL FORGING OPERATIONS §55
placed in correct alinement and two punch marks should be
made on the frame, on opposite sides of the break, but far enough
from it so as not to be covered by the mold. The punch marks
enable a trammel to be used to test the accuracy of alinement
when the weld has been completed. The jack b is inserted in
the jaw and the break is forced open about j inch, to allow
for contraction when the metal at the weld cools. The exact
Fig. 31
ai-noimt of contraction depends on the width of the collar of
metal around the weld, and therefore judgment must be used
in making the necessary allowance.
50. The mold that is built around the break must be
shaped so as to leave a collar of steel around the weld. This
collar should be thickest directly over the break and should
overlap the break at least 1 inch on each side. To make the
§ 55 SPECIAL FORGING OPERATIONS 39
recess in the mold, a pattern of yellow wax is built up around
the break, as shown at c, Fig. 31 (6), of the same size and shape
as the desired collar. The opening or break is also filled with
this wax. Then the mold box is secured in place around the
broken frame and the mold is rammed up around the wax and
the frame. The mold is made of a mixture composed of equal
parts of fire sand, good fireclay, and ground firebrick. These
materials are mixed while dry and then just enough water is
added to make the mixture pack well. The openings for the
pouring gate and the riser are made by setting in wooden pins
of the proper form. A cross-section of the mold is shown in (c),
in which d is the pouring gate, e the riser, and/ a channel for the
insertion of a heating torch. The wax g surrounds the frame k.
The combined volumes of the gate and riser should equal the
volume of the collar. The thermit steel should not be allowed
to wash, or strike directly against, the ends of the frame during
pouring; therefore, the gate should lead to the bottom of the
mold, so that the metal will rise around the break.
51. When the mold is completed, it will appear somewhat
as shown in Fig. 31 {d), in which i is the mold box. The wooden
pins forming the gate, the riser, and the heating channel are
withdrawn from the mold and a torch / is inserted through the
heating channel. The wax is thus melted, and runs out, leaving
an opening of the desired form in the mold. The heating is
continued until the mold is thoroughly dry. The thermit
crucible k is fixed in position above the mold, at a distance of
about 4 inches and directly over the pouring gate, and is charged
with thermit. The heating by the torch is continued until the
frame at the break is at a good red heat. Then the torch is
quickly withdrawn and the hole is closed securely with a dry-
sand core, backed up by sand. The ignition powder is nowplaced on top of the thermit and ignited, the cover of the
crucible is put on, and as soon as the melting has been com-
pleted the steel is tapped from the crucible. The steel will
commence to solidify about ten minutes after pouring, at
which time the screw jack h should be eased off a bit. As the
weld continues to cool and contract, the pressure of the jack
40 SPECIAL FORGING OPERATIONS 55
Fig. 32
should be reduced gradually. The mold should not be removedfor at least two hours after pouring, and then the gate and the
riser should be trimmed off.
52. If the break oc-
curs in the lower rail of
the frame, as at a, Fig. 32,
the ends at the break are
chipped away, leaving a
gap between them.Clamp bolts b are put on
the adjoining legs and their
nuts are tightened, thus drawing the broken ends farther apart.
The mold is built up in exactly the same manner as was described
in connection with Fig. 31; but in order to prevent the frame
from drawing out of alinement, the upper rail from c to d,
Fig. 32, is heated, also, at the time the weld is made. Thebolt b, which is tightened just before the mold is poured, is
loosened gradually while the weld is cooling.
If the break occurs in a vertical leg, as at o. Fig. 33, the
metal is cut away and the jack b is used to spring the ends
apart about j inch. The mold box is fitted around the vertical
leg and the upper rail, and the mold for the steel collar is madein the same way as before. The pressure of the jack is eased
off during the cooling of the weld.
53. Welding Valve LirLk.—A broken link forming part
of the valve gear of a locomotive is shown in Fig. 34 (a). Thefractures are at a and b,
so that one side c of the
link is broken out. Tomake the repair, the ends
of the curved piece c are
trimmed off, so that, whenthe piece is carefully lined
up and clamped in posi-
tion, gaps are left as
shown in (6) at d and e. Molds are arranged at these points in
the usual way, and thermit steel is run in. The appearance of the
Fig. 33
55 SPECIAL FORGING OPERATIONS 41
repaired piece after the molds are removed is shown in (c). Thecollars of metal at / and g firmly unite the piece c to the body of
the link. After the
gates h and i are cut
off and the welds are
machined to the width
of the link, the workwill appear as in (d).
In this particular case,
the metal must be cut
away considerably at
the welds, a slight rein-
forcement being left at
the points ; and k.
Wherever possible,
however, the collars of
thermit steel should be
left in place, to give the
necessary strength. In
the case of the repaired
frame shown in Fig. 31,
for example, the collar
would be trimmed up
neatly, as shown, and
not machined.
54. Welding a Broken Shaft.—The application of
thermit to the repair of a broken shaft is shown in Fig. 35. The
Ca;
(c)
break is at a shoulder where the diameter changes from 10 to
12 inches. The metal at the break is cut away, as shown in (o).
42 SPECIAL FORGING OPERATIONS §55
leaving a space 2| inches wide between the ends. The parts
of the shaft are accurately alined and blocked in position, a
wax pattern is built around the gap, and a mold is prepared.
The weld when completed appears as in (6), in which a is the
Fig. 36
riser and b the gate sprue. It is necessary, in this case, to trim
off the collar of steel, so that the repair, when finished, will
give the shaft its original appearance, as in (c). The strength
of a weld that is made with thermit and then trimmed off to
§55 SPECIAL FORGING OPERATIONS 43
the original form and size, as at c, is from 80 to 90 per cent,
of the strength of the original material. A welding operation
of this kind, on a shaft of this size, requires about 72 hours, at
the end of which time the shaft is ready to resume service. If
the shaft must be taken down and sent away, the cost of the
repair will be much greater and the machinery of which it forms
a part will be thrown out of use, entailing further expense.
55. Welding a Flywheel Arm.—The repair of a broken
flywheel arm by the use of thermit is illustrated in Fig. 36.
The wheel is built up of eight segments, each cast solid with an
arm. The break is near the rim, across one of the arms, which
are oval in section and measure 5 inches by 12 inches. The
metal at the fracture is chipped away, as in (a), and the bolts
that hold the arm to the hub are taken out. The rim and the
arm are carefully lined and clamped, and a wax pattern is put in
44 SPECIAL FORGING OPERATIONS §55
place, as in (b). The mold is built around the arm as in (c),
and the thermit crucible is suspended by a sling a. Thetorch b is used to melt out the wax pattern and to heat the
ends to redness before the mold is poured. The completed
weld is shown in (d), with the gate c and the riser d attached.
These are cut ofif neatly and the collar is smoothed up, leaving
a ring of steel around the break.
56. Repairing a Crank-Shaft Journal.—The repair of
a 9j-inch crank-shaft of an engine broken through one of the
journals is shown in Fig. 37 (a). The shaft is removed from
the engine and the broken ends a and b are cut off close to the
shoulders of the journal. The parts are then set in Y blocks, as
Fig. 38
shown in (6), and are carefully lined. Instead of using thermit
steel to make a new journal, however, a block of steel is welded
in. This block, about 10 inches square and 16 inches long, is
set between the broken ends, as at c, and is rigidly clamped
there. End movement is prevented by the iron wedges driven
into the gaps left for the welds. Wax patterns are built around
the gaps and molds are made, after which the parts to be welded
are brought to a red heat and thermit steel is nm in. The
appearance of the work after the molds are removed is shown
in (c) , the block c being firmly welded between the ends of the
journal. The gates and risers are cut off, the shaft is put in a
lathe, and the block c and the steel collars d and e are turned
to 9j inches in diameter, forming a new journal.
57. Welding a Cast-iron Pillow-Bloek.—Another
example of the application of thermit is shown in Fig. 38, in
§ 55 SPECIAL FORGING OPERATIONS 45
which (a) illustrates a broken cast-iron pillow-block. Themetal at the break is first cut away, leaving a gap a. Thework is then blocked up and clamped firmly by the straps b and c.
A mold of the proper shape is formed in the usual way, and the
weld is made with thermit, as shown in (6). The gate and the
risers are then knocked off and the jaw is machined on the side
faces and the inside.
58. Durability of Tliermit Crucible.—The best
material for the lining of thermit crucibles is magnesia tar.
Fireclay is but a makeshift, as it usually will be destroyed byone welding operation, and must then be replaced; whereas, if
the crucible is properly lined with magnesia tar, it can be used
for from 16 to 20 operations. The lining must be tamped in
place firmly. To do this, a cast-iron cone having the sametaper as the crucible is set into the crucible shell and wedged
around the top so as to leave a space between the shell and the
cone. Magnesia tar is then rammed into this space, the tamp-
ing tool being struck good, heavy blows. The cast-iron cone is
then removed, wrapped with heavy wrapping paper or several
thicknesses of newspaper, and put back in the crucible. Thewhole is then put in an oven, brought to a red heat, and kept at
that point for at least six hours. This baking of the lining is
very important, and when it is finished, the crucible should be
allowed to cool slowly. The paper wrapping of the cast-iron
cone will be charred and the cone can be removed easily. Themagnesia thimble at the bottom, through which the thermit
steel flows when the crucible is tapped, should also be wrapped
with paper when it is inserted, to enable it to be removed
easily. It must be replaced by a fresh thimble if it is cracked
or worn away by the stream of hot steel.
59. Quantity of Thermit Required.—The composition
of thermit is such that the amount of thermit steel produced
is just half the weight of thermit used. For each cubic inch of
steel required in making the weld, therefore, 9 ounces of thermit
is required; hence, to find the weight of thermit, the following
rule should be used
:
207—11
46 SPECIAL FORGING OPERATIONS § 55
Rule.— To find the number of pounds oj thermit required for a
given weld, calculate the number oj cubic inches in the weld, includ-
ing the reinforcing collar, double this number, multiply the product
by 9, and divide that product by 16.
The reason for doubling the number of cubic inches in the
weld and the collar is to allow for the metal in the gate and the
riser; and the final product is divided by 16 to reduce it from
ounces to pounds. Thus, if a certain weld is estimated to
contain 35 cubic inches, including the collar, by applying the
rule, the weight of thermit needed is found to be
35X2X9 .r. .= 40 pounds, nearly16
60. If wax is used, as already described, in building up a
pattern for the reinforcing collar, the calculation of the weight
of thermit needed may be based on the weight of wax used.
The wax not only forms the pattern for the collar, but also fills
the gap that is cut between the ends of the piece to be welded.
If the weight of the supply of wax on hand is taken before and
after the pattern is made, the weight of wax used is the differ-
ence of the two. The weight of thermit required may then be
calculated by the following rule:
Rule.— The weight of thermit, in pounds, required for a given
weld is equal to 32 times the number of pounds of wax used in
forming the pattern.
Thus, if before building up the pattern for a thermit weld,
the weight of wax on hand is 6^ pounds, and after forming the
pattern the weight of wax remaining is 4 pounds, the weight of
wax used for the pattern is 6^— 4 = 2| pounds. Then, applying
the rule, the weight of thermit required is 32X2^ = 80 pounds.
61. Additions to Thermit.—If the weight of thermit
reqiiired for a weld is greater than 10 pounds, clean mild-steel
punchings must be mixed with the thermit, to reduce the
violence of the burning. These punchings must be free from
grease and not more than | inch in diameter. A part of the heat
developed by the burning of the thermit will be used in melting
the pimchings, and the resulting temperatiire will be reduced
§ 55 SPECIAL FORGING OPERATIONS 47
somewhat, without affecting the efficiency of the weld. Theproportion of punchings to be added increases with the amountof thermit used. For quantities of from 10 to 50 pounds of
thermit, 10 per cent, of punchings should be added; but if morethan 50 pounds of thermit is required, 15 per cent, of small
mild-steel rivets may be mixed in. These percentages are
based on weights.
62. If a cast-iron piece is to be welded with thermit, the
best results will be obtained by the use of a special mixture
made by adding to the thermit about 20 per cent, of mild-steel
punchings and 3 per cent, of feirosilicon that contains 50 per
cent, of silicon. This mixture will produce a soft, uniform
metal in the weld, and the machining of the repaired section
will not be difficult. If the weld is of such a nature that the
metal is free to expand and contract, satisfactory results can be
obtained without difficulty ; but if the break is in such a position
that the cooling of the weld sets up shrinkage stresses in adjacent
parts, trouble may be experienced through the starting of
cracks near the weld.
63. The addition of steel punchings to the thermit reduces
the quantity of thermit that must be used. As already stated,
the amount of thermit steel produced is half the weight of
thermit used. The addition of a pound of steel punchings,
therefore, will increase the amount of thermit steel to the same
extent as the addition of two pounds of thermit. Hence, whensteel punchings are to be added, the calculated weight of thermit
required must be reduced by twice the weight of punchings,
to obtain the actual weight of thermit to be used. To illustrate
this point, suppose that the weight of thermit required is
calculated to be 80 pounds. According to Art. 61, it is neces-
sary to add 15 per cent, of punchings, or .15X80=12 pounds
of punchings. This quantity contains the same amount of
steel as 2X12 = 24 pounds of thermit; therefore, the actual
weight of thermit needed is 80— 24 = 56 pounds. The mixture
of 56 pounds of thermit and 12 pounds of punchings will then
produce the same weight of molten steel as would 80 pounds
of thermit
48 SPECIAL FORGING OPERATIONS § 55
64. Care In Making Thermit Welds.—When a weld is
to be made with thermit, the metal on each side of the break
must be cleaned of all grease and dirt. If this is not done, the
grease will be bm^ned out during the heating of the mold, leaving
openings through which the molten metal may escape. Themold should be rammed up very hard, and should be at least
3 inches thick; for if the mold is not sufficiently thick and
strong, the thermit steel will cut through it, spoiling the weld,
wasting the thermit, and probably melting off uninjured parts
of the work. The mold box should be made of plate ts or j inch
in thickness, and should be bound securely by tie-rods. Thecrucible should be handled carefully, to avoid cracking the
lining; therefore, it is better to carry it about the shop than to
haul it on a truck. The thimble at the bottom should be in
good condition and properly fitted. The hole in it should not
be larger than | inch in diameter. As soon as the hole becomes
worn to this size, the thimble should be renewed.
65. Welding Pipe.—Thermit may be used successfully
for welding pipes together, end to end. The pieces to be joined
are cut off squarely and are filed so that the ends, when butted
together, will fit neatly. Two such pieces are shown at a and b,
Fig. 39 (a), the squared ends meeting snugly at c. Strong
clamps d are put on each section of pipe, at about 4 inches
from the joint c, and the wing-nuts e are screwed down until the
pipes are gripped firmly. The jaws of each clamp are slotted,
and long bolts/ are set into the slots, tying the clamps together.
The nuts g on these bolts are drilled with holes into which rods
may be set, to tighten the nuts. When the nuts g are screwed
up on the bolts /, the ends of the pieces of pipe are pressed
firmly together at c. When the pieces have been butted and
clamped as shown, the two-part cast-iron mold in (b) is put
around the ends, so that the joint c in (a) is exactly central
in the mold. The cast-iron mold, shown in (b) , has an opening a
of the correct size to fit the pipe to be welded, and is provided
with a pouring gate b.
66. After the pipes are clamped and the mold is put in place,
the thermit is ignited in the usual way. The crucible used,
§55 SPECIAL FORGING OPERATIONS 49
however, is not of the type that is tapped through the bot-
tom. Instead, it is small and shallow, with a solid bottom, andis held in a pair of tongs, so that the thermit can be poured by-
tilting the crucible. In welding pipe with thermit, the thermit
steel does not come in contact with the pipe; but it furnishes
the heat required to bring the ends of the pipe to a welding
heat. In about 20 or 30 seconds after the thermit has been
ignited, the slag in the
top of the crucible is
poured into the mold
surrounding the pipe.
The slag that flows
first adheres to the
pipe in a thin layer
that protects the pipe
from the cuttingaction of the thermit
steel, which is in the
bottom of the crucible
and is poured last. Assoon as the mold is
poured, pins are inserted in the holes in the nuts g. Fig. 39 (a), and
the two ends of the pipe are drawn together by screwing up the
nuts. The ends of the pipe will soon reach a welding heat and
become soft, and this stage can be detected by the resistance to
the ttiming of the nuts g. As soon as this point is reached, the
nuts should be given four or five quarter-turns, at the same
time, thus forcing the ends of the pipes together and completing
the weld. When cool, the mold and the clamps are removed,
after which the collar of slag may be knocked ofif very readily.
The joint will show only a slight ridge at the weld, and this
may be removed by machining, if desired.
TABLE T
WEIGHTS PER LINEAB FOOT AND AREAS OP SQUARE ANDROUND STEEL BARS
Side or
TABLE I
—(Continued)
Side or
TABLE nWEIGHTS PEB LINEAR FOOT OP SQUABE AND ROUND
WROUGHT-IBON BARS
Side orDiam-eter
TABLE inWEIGHTS PER LINEAR FOOT OP FLAT WROUGHT-IRON BARS
SPECIAL FORGING OPERATIONSSerial 1691 Edition 1
EXAMINATION QUESTIONS
(1) How can the length of the center line of an irregularly
curved piece be found?
(2) Calculate the length of stock
required to make a circular welded
ring of the size shown in Fig. I.
Ans. 30| in.
(3) Explain how a piece of angle
iron is bent by the use of bending
plates. Fig. I
(4) What is the effect of repeated heating on wrought iron
or steel?
(5) Calculate the length of straight
stock f inch thick required to make,j- the square bend shown in Figf. II.
4^ Ans. 13f in.
T
9"
^'''-
"
(6) Calculate the length of stock
required for the figure-8 link shown in
Fig. III. Ans. 1\ in.
(7) Why are heating furnaces fired
with oil or gas preferred to those fired
with coal ? Fig. Ill
(8) What care must be taken when heating structural shapes
for bending?
§55
2 SPECIAL FORGING OPERATIONS § 55
(9) Why is fireclay unsuitable as a lining for thermit
crucibles ?
(10) According to Table I, what diameter of round stock
could be used to produce a bar 2| inches square, with the least
amount of forging ? Ans. 3j in.
A link like that shown in Fig. IV is to be made. Cal-
culate the length of ^-inch stock required
for it. Ans. 6f in.
(12) What is the effect of repeated
heating on cast iron ?
(13) Calculate the length of stock
I inch square required to make a round
pin I inch in diameter and 4| inches long. Ans. 2 in.
Fig. IV
(14) If a piece of cast iron is to be welded with thermit,
what special mixture should be used?
(15) Describe how a charge of thermit in a crucible is ignited.
(16) How is the molten metal tapped from a crucible whena thermit weld is being made ?
(17) A pin like that shown in Fig. V is to be made. Whatlength of f-inch stock is required?
Ans. 6i in.,T~
(18) Describe briefly the opera- ^^""^
tion of butt-welding two pieces of
pipe by the use of thermit.
Fig. V
(19) A bar of steel 1 inch square and 10 inches long is forged
to a round bar 1 inch in diameter. What is its length after
forging? Ans. 12f in.
(20) The volume of a thermit weld, including the collar that
is to surround it, is 272 cubic inches. What weight of thermit
and .steel punchings must be used ? . f214 lb. of thermit
'146 lb. of punchings